Across:
1 Pumpkin (SQUASH) jam? (squeeze = SQUASH),
4 Barman (Senior Counsel = SC-) on drugs (-UPPERS) (SCUPPERS) messes up (SCUPPERS),
9 A Mass (amass = ACCRUE) on the radio (= homophone indicator) for sailors (‘a crew’ = ‘ACCRUE’),
10 School (S-) dinner one can bring home (-TAKE OUT) (STAKE-OUT) or secretly scrutinize while sitting in a car perhaps (STAKE-OUT),
12 Sister (DOMINICAN sister/nun) in nomadic (in nomadic = DOMINICAN) settlement (= anagram indicator),
13 Derisive look (SNEER) or dig from designer (‘dig’ from ‘designer’ = esner = SNEER),
14 Reserve (reserve = BOOK) for dealer (SALESMAN) (BOOK SALESMAN) – the one pushing volumes of the stuff (BOOK SALESMAN),
18 Is critical of those telling stories (BOOK REVIEWER) to most of those in 21 across (most of ‘books’ = BOOK) and a fair amount of (half of) the rest (half of the ‘REst’ = RE-) at The Observer (-VIEWER) (BOOK REVIEWER),
21 Opens 14 across (opens ‘book salesman’ = BOOK-) for school (-S) (BOOKS) guides (BOOKS),
22 Consequences (AFTERMATH) of foreign footballers (FA) coming back (= reversal indicator) (FA = AF-) from period (-TERM-) at (-AT-) hospital (-H) (AFTERMATH),
24 Why is brute (animal) not finished (l) (‘animal’ without ‘l’ = ANIMA-) with Tory (Tory) for the most part? (y) (‘Tory’ without ‘y’? = -TOR) (ANIMATOR) Does he have to draw you a picture! (ANIMATOR),
25 That could be straightened out better (TIDIER) as ref left terrified (‘ref’ left ‘terrified’ = triied = TIDIER),
26 Don’t mention it (NOT AT ALL) to Rod (baton) off head (b) (‘baton’ without ‘b’ = aton = NOT A-) turning up (= reversal indicator) high (tall = -T ALL) (NOT AT ALL),
27 Serve (serve = VER-ES) drunk (= anagram indicator) around midnight (mid ‘niGht’ = -G-) (VERGES) on the outskirts (VERGES).
Down:
1 Supports (STANDS BY) champions? (STANDS BY),
2 Novel (UNCOMMON) produced by a foreign (a = UN-) general (-COMMON) (UNCOMMON),
3 Reject (SPURN) idiot getting away from disruption (‘idiot’ getting away from ‘disruption’ = srupn = SPURN),
5 Gain experience (CUT ONE’S TEETH) – you might have to do this if you want to get an interview at the dentists? (CUT ONE’S TEETH),
6 Paint Saki (Paint Saki = PAKISTANI) out of place (= anagram indicator) living in Islamabad (PAKISTANI),
7 Brought to mind (EVOKED) bird (dove) flying up (= reversal indicator) (dove = EVO-D) over Kildare (-KE-) (EVOKED),
8 Tries a (tries a = SATIRE) novel (= anagram indicator), a parody of others (SATIRE),
11 What one of the gravediggers has to do in Hamlet (gravedigger in Hamlet has to ACT LIKE A FOOL) with clown’s remit (ACT LIKE A FOOL),
15 Leave The Gate at a snail’s pace (SLOW START) with stupid (SLOW) leading actor (STAR-) taking time (-T) (SLOW START),
16 A winger’s (a wingers) shot (= anagram indicator) (a wingers = SWEARING) is promising (SWEARING),
17 Old (O-) church member (Roman Catholic = -RC-) is strict (-HARD-) on self-starter (‘Self’ starter = -S) (ORCHARDS) and those with the plum jobs perhaps (ORCHARDS),
19 Pick up (OBTAIN) a bit on (a bit on) movement (= anagram indicator) (a bit on = OBTAIN),
20 Votes (votes = SOV-ET) lost (= anagram indicator) around island (-I-) (SOVIET) by old council (SOVIET),
23 Lift (RAISE) is (-IS-) in the middle of elevated (= reversal indicator) space for The Hearing (ear = RA-E) (RAISE).