Across:
1 Three goals (TREBLE) for the sound engineer to turn around (TREBLE),
4 Make public (AIR-) the wines (-PORTS) (AIRPORTS) produced by JFK and Charles de Gaulle? (AIRPORTS),
9 Celebrated (AUGUST) American (A-) upstart (‘Up’ start = -U-) from Air Force? (air force = -GUST) (AUGUST),
10 There’s no end to this (ETERNITY) entire (entire = ETERNI-) melody (= anagram indicator) by The Yardbirds, for starters (‘The Yardbirds’ for starters = -TY) (ETERNITY),
12 A loud (aloud = homophone indicator) relative (‘son’ = ‘sun’ = SUN-) is depressed (-DOWN-) in hospital (-ER) (SUNDOWNER) with the drink of late (SUNDOWNER),
13 Make a show (FEIGN) of elder from Greenfield (‘elder’ from ‘Greenfield’ = genfi = FEIGN),
14 Parcels (parcels = PACKAGE -S) around wood (DEAL-) (PACKAGE DEALS) offered to holidaymakers (PACKAGE DEALS),
18 Bars (PUBLIC HOUSES) 20 down (‘public’ = PUBLIC) from 27 across (‘houses’ = HOUSES) (PUBLIC HOUSES),
21 Type of diving (SCUBA) school (S-) in the Caribbean (-CUBA) (SCUBA),
22 Don’t find fault – it’s a favour (don’t look GIFT HORSE in the mouth) to present (GIFT) to Arabian (HORSE) (GIFT HORSE),
24 Invoice (BILL-) is charged (-ION-) to Society (-S) (BILLIONS) keeping all the banks afloat presumably (BILLIONS),
25 Takes off (SPOOFS) spy (spook) endlessly (k) (‘spook’ without ‘k’ = SPOO-) upsetting (= reversal indicator) party (Sinn Féin = SF = -FS) (SPOOFS),
26 Changed one’s mind (RECANTED) reading (R-) English- (-E-) -German philosopher (Kant) to the audience (= homophone indicator) (‘Kant’ = ‘cant’ = -CANT-) for editor (-ED) (RECANTED),
27 Takes advantage of (-USES) surprise (HO-) opening (= positional indicator) (HOUSES) for a number of families (HOUSES).
Down:
1 New (= anagram indicator) parents’ (parents = TRANSEP-) first time (first ‘Time’ = -T) (TRANSEPT) in the chapel (TRANSEPT),
2 Oriental (east = E-) suing EC (suing EC = UGENICS) boss (= anagram indicator) (EUGENICS) for distorting race relations (EUGENICS),
3 Might one be able to secure colt (LASSO) for young woman (LASS-) from Ring (-O) (LASSO),
5 One of those detained (internee) briefly (e) (‘internee’ without ‘e’ = INTERNE-) at square (-T square) eatery (CAFÉ) (INTERNET CAFÉ) providing refreshments to the surfers? (INTERNET CAFE),
6 Samples (PORTFOLIO) drink (PORT-) with duck (-O-) in filo (filo) bake (= anagram indicator) (filo = F-LIO) (PORTFOLIO),
7 Fruity snack (RAISIN) for short (e) hike (‘raise’ without ‘e’ = RAIS-) up (= reversal indicator) north (NI = -IN) (RAISIN),
8 Easy going with no ego (‘easy going’ with no ‘ego’ = asying = SAYING), in a manner of speaking (SAYING),
11 Most (t) smart (‘intelligent’ without ‘t’ = INTELLIGEN-) going to Clare (-CE) (INTELLIGENCE) for news (INTELLIGENCE),
15 Pat’s put on his back (pats on back / ADULATION) by former minor (adult = ADUL-T-) over starting aggro (starting ‘Aggro’ = -A-) and is charged (-ION) (ADULATION),
16 Takes a lot of interest (lending at high/extortionate interest rates = USURIOUS) in you and me (us) on both ends (us + us = US-US) of youth centre (‘yoUth’ centre = -U-) in Brazil (-RIO-) (USURIOUS),
17 Works out (ASSESSES) with judges (ASSESSES),
19 Lads falling off sailboards (‘lads’ falling off ‘sailboards’ = siboar = ISOBAR) – it could be the pressure staying on a line (ISOBAR),
20 Concerns the people (PUBLIC) in (‘in’ = ‘inn’ = PUB-) state (= homophone indicator) getting brief (k) taste of something (‘lick’ without ‘k’ = -LIC) (PUBLIC),
23 Beastly type (HIPPO) produces joint (HIP-) by river (River -PO) (HIPPO).