Across:
1 Pressure (P-) on paramilitaries (Ulster Freedom Fighters = -UFF-) in (-IN) (PUFFIN) flyer (PUFFIN),
4 Ghost-like, returning type (REVENANT) of veteran (veteran = REVENA-T) travelled (= anagram indicator) around pole (North Pole = -N-) (REVENANT),
9 Characters in Baltimore gone (characters in ‘Baltimore gone = OREGON) to Washington’s border (OREGON),
10 Not (not = O-NT) wrong (= anagram indicator) about father (parish priest = -PP-) with single (-ONE-) (OPPONENT) rival in Ring (OPPONENT),
12 Two men (Louis + Ian = LOUIS + IAN-) with a (-A) (LOUISIANA) Texas neighbour (LOUISIANA),
13 Commend highly (EXTOL) pals getting out of poll taxes (‘pals’ getting out of ‘poll taxes’ = oltxe = EXTOL),
14 Still perhaps, it’s a healthy drink (MINERAL WATER) in spring (MINERAL WATER),
18 Runs the school (HEADMISTRESS) in Schull (“schull = “skull” = HEAD-) – they say (= homophone indicator) for the other woman (-MISTRESS) (HEADMISTRESS),
21 Fiction (LIE-), for example (e.g. = -GE), upsets (= reversal indicator) (LIEGE) one of those in Belgium (LIEGE),
22 Can (TIN) Frank (OPEN-) Ward (-ER) (TIN OPENER) use this for spilling the beans? (TIN OPENER),
24 Update it (update it = APTITUDE) playing (= anagram indicator) with natural ability (APTITUDE),
25 Show-off (= anagram indicator) in game (in game = ENIGMA) is a mystery to others (ENIGMA),
26 Christmas Day, St Stephen’s Day (HOLIDAYS) and the rest (rest time on HOLIDAYS),
27 Vegetable (BEET-) for the foreign (the = -LE) (BEETLE), common bug (BEETLE).
Down:
1 Issues (PROBLEMS) with grim (= anagram indicator) sombre LP (sombre LP = PROBLEMS),
2 Haunt (FREQUENT) one after another (FREQUENT),
3 No wins in Wisconsin (no ‘wins’ in ‘Wisconsin’ = sconi = ICONS) for the celebrities (ICONS),
5 Illuminating declarations (EXPLANATIONS) by former (EX-) pal (pal = -PLA-) moving (= anagram indicator) places in Europe (-NATIONS) (EXPLANATIONS),
6 It’s for the beloved runners (ELOPEMENT) getting away for the match (ELOPEMENT),
7 Spies (AGENTS) American (A-) reporting (= homophone indicator) Lou (“Lou” = “loo” = -GENTS) (AGENTS),
8 Count’s (counts = TOTALS) last to (last to = TOTALS) recover (= anagram indicator),
11 Gave up on Labour (CALLED IT A DAY) and Left when it came to the time to retire (CALLED IT A DAY),
15 Part of movie (RE-EL-) on old community (European Community = -EC-) following rock ‘n’ roll (Teddy Boy = -TED) (RE-ELECTED) is returned to the house (RE-ELECTED),
16 Guy (guy/male = HE-) Henry is central (‘Henry’ central = -N) to odd (= anagram indicator) thing (thing = NIGHT) (HEN NIGHT) that’s for women only (HEN NIGHT),
17 Takes drugs (USER-) from celebrity (-NAME) (USERNAME) with online identity (USERNAME),
19 Barman (BL-) on train (teach) heading off (t) (‘teach’ without ‘t’ = -EACH) (BLEACH) to lighten up (BLEACH),
20 Learnt (learnt = RENTAL) Builder (= anagram indicator) provided temporary accommodation (RENTAL),
23 A sin leaving the Apennines (‘a sin’ leaving the ‘Apennines’ = PENNE) for dish of pasta (PENNE).