Across:
1 Reviews (= reversal indicator) bed and breakfast (B&B = -BB-) in great hall in Greece (Stoa = A-OTS) (ABBOTS) directly over a number of religious buildings (ABBOTS),
4 More forthcoming (CHATTIER) gossip (CHAT-) linked to bank (bank/layer = -TIER) (CHATTIER),
9 Illustrates lost trail (‘illustrates’ lost ‘trail’ = lustes= TUSSLE) in Donnybrook (donnybrook/row = TUSSLE),
10 Young hoodlum in New York (PUNK) linked to swing (swing/sway = ROCK) (PUNK ROCK) – the musical type (PUNK ROCK),
12 Agent (spy) isn’t finished (y) (‘spy’ without ‘y’ = -SP-) with that man (-HE-) consumed by guilt? (blame = BLA-ME) (BLASPHEME) God dammit! (BLASPHEME),
13 Finishes 6 down (finishes ‘take sides’ = SIDES) with right and left (SIDES),
14 Accommodation for the comedians (HOUSE OF CARDS) is not structurally secure (HOUSE OF CARDS),
18 Shut your eyes and eat your dinner (BLIND TASTING) out of sight? Only the connoisseur will savour this! (BLIND TASTING),
21 Let off the hook perhaps (UNPEG) by newsgroup losing rows (‘newsgroup’ losing ‘rows’ = negup = UNPEG),
22 Drunk (= anagram indicator) poteen mix (poteen mix = EXEMPTION) that’s not subject to taxes, for instance (EXEMPTION),
24 Rejects (= reversal indicator) whistleblower’s (refs = -SFER) point (compass point North = -N-) on what’s in the museum (art = TRA-) (TRANSFER) to handover (TRANSFER),
25 Thugs (BRUTES) from Brest (Brest) working (= anagram indicator) (Brest = BR-TES) around university (-U-) (BRUTES),
26 Watches (watches/minds = MIND-S) over place (-SET-) (MINDSETS) with outlooks (MINDSETS),
27 Had a phobia (FEARED) of American agent (Fed = FE-D) welcoming challenge (dare) starting off (d) (‘dare’ without ‘d’ = -ARE-) (FEARED).
Down:
1 Novel (= anagram indicator) about (about = AUTOB-) a household name opens (‘B Household Name’ opens = -AHN) (AUTOBAHN) The Road – the German translation (AUTOBAHN),
2 Work hard (BUST A GUT) for bighead (‘Big’ head = B-) opening tavern (opening ‘Tavern’ = -T-) in America (USA = -US- A) with retiring (= reverse indicator) Yank (yank/tug = GUT) (BUST A GUT),
3 Head (T-IP) introduces university (University of Limerick = -UL-) (TULIP) to one of Lily’s family (TULIP),
5 Parliamentary celebrations (HOUSE PARTIES) at the start of 14 across (start of ‘house of cards’ = HOUSE) for Sinn Féin and The Greens (PARTIES) (HOUSE PARTIES),
6 Profit (TAKE) on salad and chips (SIDES) (TAKE SIDES) to support one of the parties (TAKE SIDES),
7 Exchanged for money (-SOLD-) in Ireland (.ie = I-E) (ISOLDE) by Tristan’s lover (ISOLDE),
8 Disreputable debonair (RAKISH) artist (RA-) at The Lighthouse, Dublin (-KISH lighthouse, Dublin) (RAKISH),
11 Trim (l) market (‘sell’ without ‘l’ = SEL-) on Friday (-F) provides attraction (INTEREST) (SELF-INTEREST) that’s to one’s personal advantage (SELF-INTEREST),
15 Sings the praises of (EULOGISES) Engineering (E-) Chronicle (-LOG-) inserted in new (= anagram indicator) issue (issue = -U-ISES) (EULOGISES),
16 Ulster (-NI-) consumed by address (mister = MI-STER) (MINISTER) heard in the church (MINISTER),
17 Worried about (AGONISED) sea dog in (sea dog in) trouble (= anagram indicator) (sea dog in = AGONISED),
19 Business (CUSTOM) practice? (CUSTOM),
20 Portuguese neighbour (SP-AIN) welcomes recipe (-R-) (SPRAIN) that comes with a twist (SPRAIN),
23 Agnes Rupert’s holding (‘agnES RUPerts’ holding = esrup) back (= reverse indicator) (esrup = PURSE) where you might expect to find change (PURSE).