(Please click here for this same blog but with a picture quiz added. Please do NOT post hereinbelow any comment relating to the picture quiz. Thank you.) It wasn’t plain sailing at the start, but I finally finished it. Thanks to Jason. Definitions are underlined in the clues.
Across
1 Item of luggage? Article getting common check out (4,3,5)
CASE THE JOINT : CASE(an item of luggage) + THE(an article in grammar) plus(getting) JOINT(in common with others, as in “joint ownership of…”).
10 One’s on the way out of blind alley (7)
IMPASSE : I’M(contraction of I am;one is;one’s) + PASSE(on the way out;has-been).
Defn: … or a passage having no exit;a cul-de-sac.
11 Comrade‘s newt is in catalogue (7)
LEFTIST : EFT(a juvenile newt) contained in(is in) LIST(a catalogue).
Defn: One who might call his political bedfellow a comrade.
12 Little Napoleon shifting Earl to the front finds wood? (5)
EBONY : BONEY(shortened nickname for Napoleon Bonaparte) with E(abbrev. for “Earl”) placed first(shifting … to the front).
13 Exciting bloke made tiny changes (8)
DYNAMITE : Anagram of(… changes) MADE TINY.
15 Old writer reportedly to snatch feasible time when anything goes (4,6)
OPEN SEASON : O(abbrev. for “old”) + PEN(a writing instrument) + homophone of(reportedly) “seize”(to snatch) + ON(feasible, usually used in the negative sense, as in “your proposal is not on”;not workable).
16 Blister? Cyclist needs a hundred and fifty one less (4)
CYST : “Cyclist” minus(needs … less) “CLI”(Roman numeral for a hundred and fifty one).
Defn: … or, more exactly, a blister-like abnormal growth under the skin.
18 Proof goof in publicity poetry (4)
TYPO : Hidden in(in) “publicity poetry“.
Defn: Short for an error in printed text.
20 This place’s set for promotion (5,5)
SALES PITCH : Anagram of(… set) THIS PLACE’S.
22 Walk all over cold meadow first and get lost (5,3)
CLEAR OUT : ROUT(to defeat totally;to walk all over) placed after(… first) [ C(abbrev. for “cold”) + LEA(a meadow;an area of grassland) ].
Defn: … as an exclamation.
24 Dance is back in drag – no chance! (5)
CONGA : Hidden in(in) reversal of(back) “drag – no chance“.
26 Large pet? Pet belonging to mum? (7)
MASTIFF : MA’S(possessive pronoun of “ma”;belonging to mother) TIFF(a disagreement, especially between friends or lovers, which could, I guess, cause or be caused by a pet;a fit of sulking).
Defn: …, of the canine variety.
The largest of the large?

27 Runner who harasses somebody more like King Henry V!? (7)
HARRIER : Triple defn: 1st: … on a cross-country team; and 2nd: One who harasses; and 3: Cryptic. Somebody more like Harry could be said to be Harrier (the superlative), and King Henry V when he was a lad was called Prince Harry in Shakespeare’s Henry IV plays.
28 Policies about one upsetting a cinch (5,7)
PLAIN SAILING : PLANS(policies;courses of action adopted or proposed by an organization or individual, or as in “an insurance policy”;insurance plan) containing(about) I(Roman numeral for “one”) + AILING(upsetting;troubling someone).
Defn: An easy task.
Down
2 Give the nod to handy program range (7)
APPROVE : APP(a handy computer program for mobile devices) + ROVE(to range;to wander).
3 Art from French, for example, is beginning to thrill author (8)
ESSAYIST : ES(French for “are”, an archaic English word for which is “art”) + SAY(for example, as in, say, “it looked like a big dog, say, a mastiff”) + IS + the 1st letter of(beginning to) “thrill“.
4 Hard going over slippery cove – untrustworthy sort (4)
HEEL : H(abbrev. for “hard”) placed above(going over, in a down clue) EEL(an untrustworthy man;a slippery cove).
Defn: …, like a slippery cove.
I’m hard-pressed to find an example of “h” as an abbrev. for “hard”, except in combination, eg. “hard disc drive”.
5 Flag day out received and understood (5,5)
JOLLY ROGER : JOLLY(a day out;an outing supposedly for business, but really for enjoyment) + ROGER(in radio communications, used to indicate that the message has been received and understood).
6 Somehow fair to accept note in Latin below (5)
INFRA : Anagram of(Somehow) FAIR contained in(to accept) N(abbrev. for “note”).
7 One fool in attempt for term in Oxford or Cambridge college (7)
TRINITY : [I (Roman numeral for “one”) + NIT(a fool) ] contained in(n) TRY(an attempt at something).
8 Survey scrupulously with this, choice also: male in fixing botch (4-5,4)
FINE-TOOTH COMB : FINE(choice;one of the best) + TOO(also;in addition) + [ M(abbrev. for “male”) contained in(in) anagram of(fixing) BOTCH].
Defn: The “this” in the clue.
9 Rate the tester turning out this shopper’s distraction (6,7)
STREET THEATRE : Anagram of(… turning out) RATE THE TESTER.
14 Urchin, kid with a cake (10)
RAGAMUFFIN : RAG(to kid;to tease) plus(with) A + MUFFIN(a small domed sponge cake).
17 Casper, sadly getting tense, left – like a ghost (8)
SPECTRAL : Anagram of(…, sadly) CASPER
containing(getting) T(abbrev. for “tense”, in grammar) + L(abbrev. for “left”).
19 Present drink as exercise (5-2)
PRESS-UP : PRES(abbrev. for “present”) + SUP(to drink).
The only usage I found for “pres” was as a notation that someone was present, say, at a meeting.
21 Blasted tonnes I picked up garnering latent hostility (7)
TENSION : Anagram of(Blasted) TONNES I.
23 Girl’s boosted by a dip (5)
RAITA : RITA(a girl) containing(…’s boosted by) A.

25 Saturn’s fifth with reduced warmth? (4)
RHEA : The 5th letter of(…’s fifth) “Saturn” plus(with) “heat”(warmth) minus its last letter (reduced …).
Defn: Also known as Saturn V, one of Saturn’s moons,which would not have much warmth. A WIWD (wordplay intertwined with definition) clue.
(Please do NOT post hereinbelow any comment relating to the picture quiz. Thank you.)
Nice puzzle – tougher than it looked at first – but not too much so.
Re 4d – H = hard comes from pencils – where B is soft.
Thanks both.
Isn’t 25d a full &lit?
RHEA is Saturn’s fifth moon – working outwards – sometimes referred to as Saturn V (I got all that from wikipedia BTW) – it’s also icy (that too)
… so there’s the whole surface giving a definition. The whole surface is also used by the wordplay – QED.
Or is WIWD a scchuaism for &lit? I asked Mr Google and all the hits I got on this site were scchua blogs.
Thanks Jolly Swagman. Had forgotten about the graphite pencils.
I used WIWD, deliberately to avoid discussion as to whether it was a partial or total &lit. A lot of such discussion, sometimes heated, had taken place about whether a clue was indeed an &lit or not. So now I leave it to the reader what he/she wants to make of it. I only point out where wordplay might be considered a part of the defn, as in pointing out “the lack of warmth” in this instance.
Thanks scchua and Jason.
This setter is certainly on a different wavelength to others in the FT stable and so it took a while to get going.
I couldn’t understand the ES at 3dn and assumed a mistaken lack of definition at 25 so really appreciate your help scchua.
I thought that 1ac and 5dn were particularly good.
Thanks Jason and scchua
Found this pretty straightforward in a couple of shortish sessions when I could grab them this morning. Quite enjoyed it though !
Was a lot of variety of clue types used throughout the puzzle and particularly liked the long ones. Took a while to fathom what Rhea had to do with Saturn’s fifth, until I looked up to see that it was the fifth furthest out from it.
Finished in the NE corner with OPEN SEASON (which took a while to realise the homophone), ESSAYIST (where had to remember the ‘art=are’ trick … and convert to French) ad IMPASSE (which held me up with the I’M PASSE parsing for a bit).