Across:
1 Take steps (act = AC-T) around church (Church of England = -CE-) heading for nave (heading for ‘Nave’ = -N-) (ACCENT) with sign of stress (ACCENT),
4 Sounds like (= homophone indicator) Beany or Barney perhaps (“Batchelors” peas & beans perhaps = Beany or Barney = “batchelor” = BACHELOR) hasn’t got a regular mate (BACHELOR),
9 Left out (l) French wine (clarets) (‘claret’s without ‘l’ = CARETS) from Marks – an indication to add in something else (editing mark to add in text = ? = CARETS),
10 Upsets (= reversal indicator) English (-E) Fellow (man = NAM-) and most of (t) the rest (‘rest’ without ‘t’ = res = -SER) at university (U-) (USERNAME) with online identity (USERNAME),
12 Part of the golf course (ROUGH) proposal (PLAN) (ROUGH PLAN) written on the back of a cigarette pack, for instance (ROUGH PLAN),
13 Some remarkable aversion (some ‘remarkabLE AVErsion’ = LEAVE) to what holidaymakers are liable to take (time off / LEAVE),
14 Volte-face (CHANGE OF MIND) as a result of lobotomy perhaps (CHANGE OF MIND),
18 Choosing the wood perhaps (choosing the wood golf club = DRIVING) on the mountains (RANGE) (DRIVING RANGE) popular with the swingers (DRIVING RANGE),
21 Advertised without dates (‘advertised’ without ‘dates’ = dveri = DRIVE) for excursion (DRIVE),
22 Terrible (= anagram indicator) omen (omen = MONE-) in dodgy (seedy = SEED -Y) (SEED MONEY) finances for eventual opening of business (SEED MONEY),
24 Refuse to go into this (BIN LINER holds the refuse/rubbish) with criminal (= anagram indicator) in Berlin (in Berlin = BIN LINER),
25 Fellows (MEN-) from academy (-A-) involved in the Italian (‘the’ Italian = il = -I-L) (MENIAL) routine (MENIAL),
26 Greene is (Greene is) going all over the place (= anagram indicator) (Greene is = ENERGISE) to get a shot in the arm (ENERGISE),
27 Country (USA-) ends appalling practice nowadays (ends ‘appallinG practicE nowadayS’ = -GES) (USAGES) of accepted conventions (USAGES).
Down:
1 Exactitude (ACCURACY) of American (A-) university (University College Cork = UCC) upset (= reverse indicator) (UCC = -CCU-) by smutty type (-RACY) (ACCURACY),
2 Crucial (crucial = CIRCULA-) play (= anagram indicator) with right (-R) (CIRCULAR) message for wider distribution (CIRCULAR),
3 Mark (mark = NOTCH) of deal from Decathlon? (‘deal’ from ‘Decathlon’ = cthon = NOTCH),
5 Daydreaming (ABSENT-MINDED) when not in school? (‘absent’ = ABSENT-) Took umbrage with that! (-MINDED) (ABSENT-MINDED)
6 Compromising (HARDLINE-) writing (from the 3Rs = -R) (HARDLINER) from political zealot (HARDLINER),
7 A small (a small) train (= anagram indicator) (a small = LLAMAS) with pack animals (LLAMAS),
8 Created a stink (REEKED), as had the bang of Benjy (REEKED),
11 Coming from the heart (BLOOD VESSELS) of family (BLOOD) going overseas (VESSELS) (BLOOD VESSELS),
15 Growing concern (GARDENING) for those tending to plot (GARDENING),
16 Organisation (UN-) is being wound up perhaps (-ENDING) (UNENDING) and it’s taking an age (UNENDING),
17 Tight (= anagram indicator) secrecy (secrecy = RECYC-ES) around port (port/left = -L-) (RECYCLES) plays into The Green’s agenda perhaps (RECYCLES)
19 Recalls (= reverse indicator) the foreign (‘the’ Spanish = el = -LE) offer (bid = -DIB-) is close to obscene (close to ‘obscenE’ = E-) (EDIBLE) and not hard to take (EDIBLE),
20 Is about to join The Union (FIANCÉ) working (= anagram indicator) in café (in café = FIANCÉ),
23 Turns up (= reverse indicator) Old Bob (‘old bob’ = shilling = -S) is a supporter of golf (tee = -EET-) and most top (‘Most’ top = M-) (MEETS) athletic events (MEETS).