Thank you to Mog. Definitions are underlined in the clues.
Across
1. Bull given snip chasing male vet? (5)
MEDIC : “edict”(bull/an official order issued by the Pope) minus its last letter(given snip) placed after(chasing) M(abbrev. for “male”).
Defn: … or veterinary surgeon, an example of/? a medical practitioner).
4. Keen to maintain excellent standard up to the midriff (5-4)
WAIST-DEEP : WEEP(to keen/wail in grief for a dead person) containing(to maintain) [AI(A1/first class/excellent, with the Roman numeral substitution) + STD(abbrev. for “standard”) ].
9. All the best Argentine red, then English port (7)
CHEERIO : CHE(Guevara, a red/Marxist born in Argentina) plus(then) E(abbrev. for “English”) + RIO(Brazilian port).
Defn: Like …, an expression of good wishes on parting.
10. Tackle drinks in a pair of pyjamas when study’s delayed? (3,4)
GAP YEAR : GEAR(tackle/equipment for a particular task) containing(drinks in) [A + 1st 2 letters of(pair of) “pyjamas” ].
Defn: A period when a student takes a period, usually an academic year, off from studies.
11. Show George, perhaps, helping to end devil (13)
DEMONSTRATION : [ ST(abbrev. for “saint”, an example of which/perhaps, is St. George) + RATION(a helping/an allotted amount) ] placed after(to end) DEMON(a devil/an evil spirit).
14. Call to lover overheard in wind? (4)
OBOE : Homophone of(… overheard) [ Oh, beau! ](a call to one’s lover).
Defn: An instrument in the wind/woodwind section of an orchestra.
15. Spy dog smuggles contents of plan in little bits (9)
MOLECULAR : MOLE(a spy occupying an important position in an enemy’s security organisations) + CUR(an aggressive or dirty dog) containing(smuggles) inner letters of(contents of) “plan“.
18. Opening of Lancashire furniture chain’s trending immediately (4,1,4)
LIKE A SHOT : 1st letter of(Opening of) “Lancashire” + IKEA(the Swedish retail furniture chain) + HOT(trending now/in current fashion).
19. American pier not quite in water (4)
AQUA : A(abbrev. for “American”) + “quay”(a pier/a platform projecting into water for loading and unloading ships) minus its last letter(not quite).
21. Way to work around imposed changes (5,8)
MODUS OPERANDI : Anagram of(… changes) AROUND IMPOSED.
24. Keeping in fashion behind bar for the most part (7)
STORAGE : RAGE(that which is in fashion/in vogue) placed after(behind) “stop”(to bar/to prevent) minus its last letter(for the most part).
26. Oddly miss old Islay, upland island for hopping (4,3)
LILY PAD : Letters in the odd positions deleted from(Oddly miss) “old Islay, upland“.
Defn: What you might describe as an island/a thing surrounded by water for frogs to hop to and from.

27. Field where they saw grouse coming in (9)
CARPENTRY : CARP(to grouse/complain about) + ENTRY(act of coming in).
Defn: …/an area of activity in which tools like various saws are used.
28. Play the crab, primarily sniping and doing little (5)
SIDLE : 1st letter of(primarily) “sniping” plus(and) IDLE(doing little or nothing/inactive).
Defn: Play/behave like the crab, specifically, walk sideways furtively.
Down
1. Blades ground for the kitchen staff (4)
MACE : Double defn: 1st: The outer covering of nutmegs, which look like blades/have the shape of leaves when detached, are ground to make this spice used in the kitchen (I can’t think of anything else that might fit); and 2: … of the ceremonial kind or of a kind of weapon.
1: Blades before and after being ground:
and 2: Ceremonial staff: 
2. Drawn after capturing rook stranded up top? (11)
DREADLOCKED : DEADLOCKED(drawn/with opposing sides having the same scores) containing(capturing) R(abbrev. for “rook”, in chess notation).
Defn: With hair twisted in strands.

3. Plate in church boosting capital? Quite the opposite (6)
CHROME : CH(abbrev. for “church”) placed above(boosting …? Quite the opposite, in a down clue) ROME(capital city of Italy).
4. Spirit with punch seen around delta city (4,5)
WOOD NYMPH : W(abbrev. for “with”) + OOMPH(punch/the power to impress or attract, taking your breath away in the process) containing(seen around) [ D(letter represented by “delta” in the phonetic alphabet) + NY(abbrev. for “New York”, city in the USA) ].
5. Croon head off to uplifting cast piece (5)
INGOT : “sing”(… a soft low voice/to croon) minus its 1st letter(head off) + reversal of(… uplifting, in a down clue) TO.
Defn: … of solid metal.
6. Adept manoeuvres with cane, largely (3,5)
TAP DANCE : Anagram of(… manoeuvres) [ ADEPT plus(with) “cane” minus its last letter(largely) ].
Defn: …/rhythmic steps performed wearing shoes with metal pieces attached to the soles. And with a cane sometimes.
… more here: https://www.readersdigest.co.uk/culture/film-tv/10-best-movie-tap-dances
7. Matriarch at no point removes clothes (3)
EVE : “never”(at no point/not ever) minus its 1st and last letters(removes clothes).
Defn: According to the Bible, the very first matriarch/a venerable woman.
8. Dad took off, or mum left? Hard to explain (10)
PARANORMAL : PA(informal term for one’s dad/father) + RAN(took off/hurried away) + OR + MA(informal term for one’s mum/mother) + L(la. “left”).
Defn: …/beyond the scope of normal scientific understanding.
12. Unprepared setter’s going to crack into deep cryptic (3-8)
ILL-EQUIPPED : I’LL(I will/setter is/setter’s going to, with the setter using the self-referential pronoun) + [ QUIP(a crack/a joke) contained in(into) anagram of(… cryptic) DEEP ].
13. Drum with scowl, struggling to grasp current genre (5,5)
WORLD MUSIC : Anagram of(…, struggling) [ DRUM plus(with) SCOWL ] containing(to grasp) I(symbol for electrical current in physics).
Defn: … of music from non-Western coutries.
16. Really sozzled earl fronting political protest (9)
LITERALLY : LIT(sozzled/totally drunk) + E(abbrev. for “earl”) placed above(fronting, in a down clue) RALLY(a gathering of people making a political protest).
17. Article about milk had to turn people green (8)
NAUSEATE : Reversal of(… about) AN(article in grammar) + USE(to milk/to exploit) + ATE(had/took in food).
Defn: …/to make them look pale and sickly and wanting to retch.
20. Old folk? They’re sometimes right (6)
ANGLES : Double defn: 1st: …, specifically a Germanic people who came to England); and 2nd: In geometry, the space between 2 intersecting lines, in this case, measuring 90 degrees.
22. Fold suit and tie that is left out (5)
PLEAT : PLEA(a suit/a petition/a formal request) plus(and) “tie” minus(left out) “ie”(abbrev. for “id est”/that is).
23. Sharpness put wife off piece of cheddar (4)
EDGE : “w”(abbrev. for “wife”) deleted from(put … off) “wedge”(a piece in the shape of a well, wedge, in this case a piece of cheddar cheese).
Defn: …/an intense and biting quality.
25. Crew need underground rock for broadcast (3)
OAR : Homophone of(… for broadcast) “ore”(underground rock which is mined and then worked to yield valuable material).
Defn: A member of the crew of a rowing boat.
Thanks, Mog and scchua!
What a blog!
MACE
Your parsing seems perfect.
TAP DANCE
I agree that the ‘largely’ may not be a great fit in the Def.
Nonetheless, this looks like an intended &lit. Right (of course, your parsing points to that but it isn’t explicitly mentioned)?
Thanks scchua and Mog.
Gave up on DREADLOCKED and NAUSEATE with all crossers. Just couldn’t see them. Great puzzle, otherwise.
MEDIC
CHEERIO
OBOE
WOOD NYMPH
PARANORMAL
make my list.
Excellent puzzle and blog. Took ages but worth it. MACE takes my cake from many tasty clues. I started with Oooh for 14a. Well, that’s what mine says to me. Just kidding. Wouldn’t parse, so I went for ‘Oh Boy’ as a sort of homophone for OBOE. Oh well. Thanks scchua and Mog. Made my Sunday so far.
I concur with KVa that TAP DANCE is an &lit. That together with MODUS OPERANDI & PARANORMAL were my favourites in a most enjoyable crossword. The SW took a bit of working out, I thought.
Splendid puzzle from Mog on his second outing. I recall the first was a theme that was unfamiliar to me. This one, freed from theme constraints, is better in my book with loads of creative ideas. Plenty that earned ticks as I went through with the highlights being CHEERIO, DEMONSTRATION, LIKE A SHOT, MOLECULAR, MODUS OPERANDI, MACE, WOOD NYMPH, TAP DANCE and ANGLES. Which is quite a list.
Thanks Mog and scchua
Here’s a different TAP DANCE double act – Gene Wilder & Peter Boyle performing Irving Berlin’s Puttin’ On The Ritz from Mel Brooks’ Young Frankenstein(1974).
https://www.youtube.com/watch?v=2ernUF5sP9U
They both have canes and one of them is large.
V. enjoyable second puzzle from Mog after his first Super Mario Bros. themed offering in May. Not easy, but all perfectly fair, though I couldn’t parse the ‘George, perhaps’ bit of DEMONSTRATION. For 25d, I had ‘Crew need’ as the def for OAR, ie something which a (rowing) crew needs. I admit to thinking of “malbec” when I saw ‘Argentinian red’ until crossword land’s favourite revolutionary was revealed with the help of crossers. I liked ‘in little bits’ for MOLECULAR and the TAP DANCE &lit (or it would do as an &lit for me); thanks for the links, scchua and FrankieG @6.
CHROME and EDGE in the same puzzle; coincidence?
Thanks to Mog and scchua
There’s an AQUA web browser as well.
Excellent crossword – thanks to Mog and scchua.
What an excellent puzzle from Mog, greatly enjoyed here. Long tick list here with CHEERIO, LIKE A SHOT, PARANORMAL, LITERALLY and NAUSEATE vying for the rosettes.
Many thanks, Mog, and thanks to scchua for a nicely illustrated blog – I’m sure those little extras take time but they’re greatly appreciated.
WordPlodder @7 and DuncT @8: you may be onto something. There is a web-related thing called CHEERIO and one called OBOE.
… and EVE, MACE, ANGLE and possibly OARS. Whatever they are referencing is way beyond my technical pay grade but they all come up as related to web-browsing. This puzzle keeps on giving and, as a result, keeps on rising in my estimation.
I also found web software called LILYPAD (and we have IE and IOS at the tops of columns three and five – but that’s maybe stretching things a bit too far).
Thanks Mog for a splendid crossword. I started off slowly and I thought I would abandon ship but I’m glad I didn’t. I had many favourites including MEDIC, CHEERIO, GAP YEAR, MOLECULAR, MODUS OPERANDI, DREADLOCKED, PARANORMAL, and LITERALLY. (While liking the clue for LITERALLY I’m getting increasingly annoyed with the inappropriate overuse of this word in modern conversation.) My only parsing problem was OBOE. Thanks scchua for the richly illustrated blog.
so, so good – too many great clues to list, but CARPENTRY and PARANORMAL especially
MODUS OPERANDI
Bring back Netscape Navigator
STORAGE
Sofamore @ 3 and TS @ 13 .
The homophone I think is Oh Beau which does work.
Great puzzle that kept me occupied for a fair part of the afternoon taking my mind away from Thursday’s knee replacement op .
Thanks, scchua, for the lovely blog, and everybody else for the kind words. I’m glad folks enjoyed the puzzle.
I can report, regrettably, that the theme that many of you have unearthed in the grid is a complete coincidence, but it’s brightened my day to see the whole thing unfold. I hope to recreate the feat on purpose sometime in the future!
Eeek, got about five clues and have up. Nightmarishly hard!