Across:
1 Bill’s (bills = LIB-LS) breakdown (= anagram indicator) over sweetheart (‘swEet’ heart = -E-) (LIBELS) providing smears in newspapers (LIBELS),
4 Completely clean (SPOTLESS) of drugs (-POT-) after (= positional indicator) first sentence (first ‘Sentence’ = -S-) for smaller amount (-LESS) (SPOTLESS),
9 It’s limited (MEAGRE) to characters involved in unwholesome agreement (characters involved in ‘unwholesoME AGREement’ = MEAGRE),
10 Give away (divulge) clip (e) (‘divulge’ without ‘e’ = DIVULG-) journalist (-ED) (DIVULGED) made public (DIVULGED),
12 Lease (RENT) area (A) that’s not rocky (FLAT) (RENT A FLAT) and temporarily turn it into a home (RENT A FLAT),
13 See the light without the 1ST (‘see the light’ without ‘the ist’= eelgh = HEGEL) philosopher (HEGEL),
14 It’s for airing (CLOTHES HORSE) jumpers (CLOTHES) found in the stable (HORSE) (CLOTHES HORSE),
18 Set-up for anyone getting into drugs trade (drugs trade = JOINT VENTURE) business incorporating the Camorra and Ndrangheta, for example (JOINT VENTURE),
21 Paramilitaries (IRA-) reject (= reversal indicator) measure of intelligence (IQ = -QI) (IRAQI) from Middle East resident (IRAQI),
22 Places great value on (TREASURES) Reuters’ (Reuters = TRE- URES) shock (= anagram indicator) over a (-A-) story initially (‘Story’ initially = -S) (TREASURES),
24 Protest vigorously? (UP IN ARMS) Sounds like a position childish person would take! (UP IN ARMS),
25 Opens diner, eatery (opens ‘Diner Eatery’ = DE-), outlet (-DUCT) (DEDUCT) and takeaway (DEDUCT),
26 Have another look at it (REASSESS), as reading (R-) eases (eases = EASSE-) mayhem (= anagram indicator) on ship (-SS) (REASSESS),
27 Slips (SLIDES) in playground (SLIDES).
Down:
1 Colourful type (LIME-) of building unit (brick) that needs no introduction (b) (‘brick’ without ‘b’ = -RICK) (LIMERICK) to one of those in Munster (LIMERICK),
2 British (B-) weather forecast (-RAIN) on the telly (BOX) (BRAIN BOX) produced by a headcase (BRAINBOX),
3 Sample of popular variety (sample of ‘popuLAR VAriety’ = LARVA) for grub (LARVA)
5 Convictions (POINTS OF VIEW) for breaking speed limit (POINTS) going around (O-) French (-F) landscape (VIEW) (POINTS OF VIEW),
6 Mentions briefly (TOUCHES ON) in a sense (TOUCH-), Oriental (east = -E-) relative (-S ON) (TOUCHES ON),
7 Employ (ENGAGE) part of Halloween gag explicitly (part of ‘HalloweEN GAG Explicitly’ = ENGAGE),
8 Some initially (‘Some’ initially = S-) confuse (-ADDLE) (SADDLE) the sheepish type’s joint (SADDLE of lamb/sheepish type’s joint),
11 Type of chateau (CLOS-) in (-IN-) German capital (‘German’ capital = -G) with bats (= anagram indicator), mites (mites = TIMES) (CLOSING TIMES) and types that end trading (CLOSING TIMES),
15 Looking back (= reversal indicator), slow type (snail = -LI-ANS) goes around general (-G-) office (-O-) to surprise (Oh = HO-) (HOOLIGANS) troublemakers (HOOLIGANS),
16 Most of (f) the foam (‘surf’ without ‘f’ = SUR-) on stout (-ROUND) (SURROUND) in Ring (SURROUND),
17 Network (WEB-) refers to (‘cites’ = ‘sites’ = -SITES) reports (= homophone indicator) (WEBSITES) of destinations for surfers (WEBSITES),
19 A glass of whiskey (LIQUOR) for all sorts (Liquorice All Sorts) without ice? (‘liquorice’ without ‘ice’ = LIQUOR),
20 Paint a (paint a = PATINA) model (= anagram indicator) from glossy film (gloss/sheen on wood = PATINA),
23 First morsel (first ‘Morsel’ = -M-) consumed by hawk (sell = S-ELL) (SMELL), in a sense (SMELL).