Across:
1 Straight away (PRONTO) letters at the end of the page (please turn over = PTO = P-TO) about Press (iron) start to disappear (i) (‘iron’ without ‘i’ = -RON-) (PRONTO),
4 Praises (ACCLAIMS) a (A-) head of clan (head of ‘clan’ = -C-) from States (states/declares = -CLAIMS) (ACCLAIMS),
9 Foreign (= anagram indicator) squire (squire = RISQUé) is a racy sort (RISQUé),
10 Vile (= anagram indicator) green tea (green tea = TEENAGER) will need a few years to mature (TEENAGER),
12 Nothing (NAUGHT-) to do with Irish (-I-) and English (-E-) writing (from the 3Rs = -R) (NAUGHTIER) is more mischievous (NAUGHTIER),
13 Atheist loses it (‘atheist’ loses ‘it’ = athes = HASTE) in Rush (rush = HASTE),
14 Presumably, if you do drugs you’ll need this (PRESCRIPTION) to give to drug dealer for your supply (PRESCRIPTION),
18 Rank (FIELD MARSHAL) pasture (FIELD) to get into order (MARSHAL) (FIELD MARSHAL),
21 Draft treatment perhaps (draft/beer ON TAP) of new (= anagram indicator) Panto (Panto = ON TAP),
22 Bare tyres (bare tyres = BETRAYERS)? Sorry (= anagram indicator) – they’ve sold out! (BETRAYERS),
24 They lose sleep (WORRIERS) over (= reversal indicator) argument (row = WOR-), losing the head (c) with newsmen shouting on the street (town criers) (‘criers’ without ‘c’ = -RIERS) (WORRIERS),
25 Path to (path to = TOP HAT) complex (= anagram indicator) is by the milliner’s presumably (TOP HAT is by/created by the milliners),
26 Christmas callers (The Magi = WISE GUYS) from the Mafia (Mafia ‘made man’ = goodfella/wiseguy = WISE GUYS),
27 It’s important (KEY-) father (Pa = -PA-) contacts department (-D) (KEYPAD) on the phone (KEYPAD).
Down:
1 Norm (PAR-) takes short cuts (-SNIPS) (PARSNIPS) from the allotment (PARSNIPS),
2 In the end (= positional indicator), preserved (-CURED) Capital’s old building site (capitals ‘old building site’ = OBS-) (OBSCURED) hidden from view (OBSCURED),
3 It can be hard (TOUGH) for enemies leaving meeting house (‘enemies’ leaving ‘meeting house’ = tghou = TOUGH),
5 Keen (C-RY) about that woman (-HER-) taking fruit (TOMATO) (CHERRY TOMATO) out of the greenhouse (CHERRY TOMATO),
6 Something for the consumers (LUNCH HOUR) to break (LUNCH HOUR),
7 Gets in (gets in = INGEST) trouble (= anagram indicator) and is put away (INGEST),
8 A number of waves (SERIES) sound (= homophone indicator) terrifying (“eerie” = “erie” -ERIE-) in boat (S-S) (SERIES),
11 Courteous (CIVIL) to The Right (LIBERTY) (CIVIL LIBERTY) for the good of the community (CIVIL LIBERTY),
15 It could be financially damaging (CRIPPLING) for Bond (bond = C-LING) holding onto last letters (-RIP-) to post (-P-) (CRIPPLING),
16 Selling wellies (SHOE SHOP) and small (S-) garden implements (-HOE S-) for spring (spring/jump = HOP) (SHOE SHOP),
17 Miss (-LOSE-) first train (first ‘train’ -T-) in Clare (C-E-) going to Dublin (-D) (CLOSETED), as shut up in private meeting (CLOSETED),
19 Prisoner (prisoner of war = POW-) expresses admiration (-WOW) (POWWOW) for US Congress? (POWWOW),
20 Ain’t leaving stationers (‘aint’ leaving the ‘stationers’ = stoers = STORES) or stockholders? (STORES),
23 Sounds like (= homophone indicator) a way out (“a door” = “ADORE”) to take pleasure in (ADORE).