Very enjoyable puzzle, some of it easy and some of it pretty tricky – something for everyone. Thanks Alberich.
I am away from home at the moment so may not be able to respond to comments until later.

| Across | ||
| 1 | SEVENTY EIGHT | 
 Bob quits firm, holding the once classic record (7-5) 
S (shilling, a bob) EVEN (quits) then TIGHT (firm) holding YE (the, once) 
 | 
| 10 | POTABLE | 
 What running water given to group of diners must be? (7) 
PO (the River Po, running water) with table (group of diners) definition is &lit 
 | 
| 11 | SHALLOT | 
 Mum has to share out vegetable (7) 
SH (quiet, mum) has ALLOT (to share out) 
 | 
| 12 | RONDO | 
 Regina’s playing party music (5) 
R (regina, abbrev) ON (playing) DO (party) 
 | 
| 13 | DERELICT | 
 Case of rogue breaking into shop’s brought to court and abandoned (8) 
RougE (edge letters, the case of) inside (breaking into) DELI (shop) with (brought to) CT (court) 
 | 
| 15 | STEEL BANDS | 
 Around middle of seventies, Slade best? Possibly, or other ensembles (5,5) 
seveNties (middle letter of) in (SLADE BEST)* anagram=possibly 
 | 
| 16 | UNDO | 
 Cancel round of sandwiches (4) 
found inside (sandwiched by) roUND Of 
 | 
| 18 | ACME | 
 One takes months to reach peak (4) 
ACE (one) contains M (months) 
 | 
| 20 | MISOGYNIST | 
 Mark is nasty nosy git and a bigot (10) 
M (mark) IS with (NOSY GIT)* anagram=nasty 
 | 
| 22 | SWEEPING | 
 A lot of delightful goods Pole acquired wholesale (8) 
SWEEt (delightful, a lot of) PI + G (two goods)  
 | 
| 24 | ISSUE | 
 Paper abandons first edition (5) 
tISSUE missing first letter 
 | 
| 26 | INTROIT | 
 Religious piece breaking tradition? Not these days (7) 
TRadITION* anagram=breaking missing AD (these days) 
 | 
| 27 | WRINGER | 
 Wife wants double for old dryer (7) 
W (wife) RINGER (double) 
 | 
| 28 | OVERESTIMATE | 
 Put too high a value on remaining property – about one million (12) 
OVER (remaining) ESTATE (property) containing (about) IM (1M, one million) 
 | 
| Down | ||
| 2 | ENTENTE | 
 XXX stripping creates friendly relations (7) 
tEN TEN TEn (XXX) missing outside letters (stripping) – very nice! 
 | 
| 3 | EMBROILS | 
 Implicates brother in rising moral filth (8) 
BRO (brother) in SLIME (moral filth) reversed (rising) 
 | 
| 4 | TEEM | 
 Before Mass, drink’s said to flow copiously (4) 
TEE sounds like (said) “tea” (drink) before M (mass) 
 | 
| 5 | EISTEDDFOD | 
 Did feted old soprano perform for song festival? (10) 
anagram (perform) of DID FETID O (old) and S (soprano) 
 | 
| 6 | GLAZE | 
 Put coating on top of granary loaf (5) 
Granary (top, first letter of) LAZE (loaf) 
 | 
| 7 | TOLKIEN | 
 Author’s family accepting welfare finally after reversal of fortune (7) 
KIN (family) contains (accepting) welfarE (final letter of) following LOT (fortune) reversed 
 | 
| 8 | SPORTSMANSHIP | 
 It’s not cricket? The opposite, even when it’s not cricket (13) 
double/cryptic definition 
 | 
| 9 | STATE OF THE ART | 
 Constable’s condition? This is the latest development we have (5,2,3,3) 
cryptic/double definition 
 | 
| 14 | MARIONETTE | 
 One’s moved by strings playing Mozart in centre regularly? That’s not unknown (10) 
anagram (playing) of MOzART (missing Z, an unknown in equations) IN and cEnTrE (regular selection of) 
 | 
| 17 | CYNICISM | 
 Heartless, cocky chap briefly is married, displaying contempt (8) 
CockY (heartless) NICk (a chap, briefly=unfinished) IS M (married) 
 | 
| 19 | MAESTRO | 
 Eminent musician left to avoid confusion, mostly (7) 
MAElSTROm (confusion, mostly=unfinished) missing L (left) 
 | 
| 21 | INSIGHT | 
 Enlightenment is expected soon (7) 
IN SIGHT (expected soon) 
 | 
| 23 | PHONE | 
 Under pressure to polish ring (5) 
HONE (to polish) follows P (pressure) 
 | 
| 25 | SWOT | 
 Drunkard imbibing whisky could be teacher’s pet? (4) 
SOT (drunkard) containing (imbibing) W (whisky, phonetic alphabet) 
 | 
*anagram
definitions are underlined
definitions are underlined
Thanks PeeDee and Alberich. A good one! 22a was my last one in – the answer seemed reasonably obvious but I struggled to parse it. Eventually I settled for SWEEt plus PI and G (both goods) containing N (pole). I wonder what Alberich intended?
Didn’t like 22ac very much but all the rest were good. Liked 10ac very much.
Thanks both
Thanks, Peedee.
I struggled with 22ac, too, and didn’t understand your G = goods. I agree with Mike C’s parsing [now].
I don’t fully get 8dn, either.
Otherwise, a thoroughly enjoyable puzzle, with some very nice constructions and witty surfaces. Many thanks to Alberich.
I go along with MikeC’s parsing of 22A (not that I got it) as I have never seen g = goods before.
Not all that happy about 9D as ‘Constable’s condition’ would lead to ‘state of the artist’.
I’m afraid that I cannot throw any further light on 8D.
Thanks to PeeDee and Alberich
Mike C is correct about 22ac. I was getting confused – not good enough.
Re 8dn – “Its just not cricket” means unsporting, so the opposite is SPORTING, and sporting can be playing sport/being fair for other sports than cricket. A bit of a Rufus/Dante clue I thought where the challenge is not to solve it but to figure out why it is cryptic.
Re 9dn “A Contstable” could be a picture by Constable as well as the artist himself, so I think 9dn works OK.
Thanks all.
Hi PeeDee
“A bit of a Rufus/Dante clue I thought where the challenge is not to solve it but to figure out why it is cryptic.”
Hmm, yes, that’s what I had concluded – not really Alberich, is it? Unless I’m [more than probably] missing something.
Yes, PeeDee, 9d would have worked better if it had said ‘A Constable’s condition’ but it didn’t.
Ernie – re 9d, crossword clues frequently omit articles before nouns, especially proper nouns. For example in 1 across it really should be “a bob” to mean a shilling not someone’s name, in 10 across it should be “The River Po” or “The Po” to be a river, “Po” on its own doesn’t make sense.
Why is Constable any different?
Only because there is a difference in meaning.
To me ‘Constable’ refers to the artist whereas ‘a Constable’ would refer to a painting by Constable.
Thanks for your input on this, PeeDee
Thanks Alberich and PeeDee
Another from the backlog pile … and what a gem this was !!!
It was one of those puzzles that you had to just keep chipping away … and generally admiring the answers when they yielded and then needing to do further work on the parsing with a number of them.
Agree with PeeDee that all of the clue stand up on there own, including both of the long down lies at 8 and 9.
Loved POTABLE as a clue and liked the complexity of MAESTRO and SWEEPING (which was my last in).