Across:
8 Dark periods (NIGHTS) from the start of 15 across (start of 'night on the tiles' = NIGHT-) to the end of the thirties (end of 'thirtieS' = -S) (NIGHTS),
9 Thought (IMAGINED) of wild (= anagram indicator) enigma (enigma = -MAGINE-) in The Papers (ID papers = I-D) (IMAGINED),
10 In around about way (= reverse indicator), heartlessly (l) exploits (milks) (‘milks’ without ‘l’ = miks = SKIM) to take some off the top (SKIM),
11 Old sailor (tar) serves up (= reverse indicator) (tar = RAT -) what fishermen caught (CATCH-) at the point (compass point East = -E-) and from bottom of oyster (bottom of ‘oysteR’ = -R) (RAT-CATCHER) trap (RAT-CATCHER),
12 Sting’s informal (stings/swindles = SET-UPS) playlists (sets = SET-S) about a wake (‘a wake’ = ‘awake’ = -UP-)? (SET-UPS),
14 Popular (IN) Red (SEA-) State (= homophone indicator) paper (‘Sun’ = ‘son’ = -SON) (IN SEASON) is available now (IN SEASON),
15 Session (NIGHT ON THE TILES) for a date with a roof worker presumably? (NIGHT ON THE TILES),
18 Dear me – it (dear me it) flourished (= anagram indicator) (dear me it = DIAMETER) in part of The Circle (DIAMETER),
20 Secure the services of (RETAIN) border’s retail chain (borders ‘RETail chAIN’ = RETAIN),
22 Accept responsibility (TAKE THE RAP) for what director produced (TAKE) finishing off (y) treatment? (‘therapy’ without ‘y’ = therap = THE RAP) (TAKE THE RAP),
24 It’s noticeable without using beacon (it’s ‘noticeable’ without using ‘beacon’ = tiel = TILE) that’s on the house (TILE),
25 Commitment (COVENANT) to a convent (a convent) body (= anagram indicator) (a convent = COVENANT),
26 Account (AC-) on tape (-CORD) (ACCORD) of agreement (ACCORD).
Down:
1 Single out (PICK-) the French ('the' French = -LE) (PICKLE) in hot water (in a PICKLE),
2 Some become happier in retirement (= reverse indicator) (some ‘becoME HAppier’ = meha = AHEM) by getting others’ attention with this (AHEM),
3 Stimulant (ESPRESSO coffee) provides energy (E-) – why should I care (so = -S-O) media (-PRESS-) is taken in (ESPRESSO),
4 Plagiarise (LIFT) from those characters at the end of 6 down (end of ‘hitch a lift’ = LIFT),
5 Sarah’s (Sarahs) problem (= anagram indicator) (Sarahs = HARASS) with Harry (harry/attack = HARASS),
6 Problem (HITCH) with American (A) pick-up (LIFT) (HITCH A LIFT) – flag down passing traffic (HITCH A LIFT),
7 Writer (PEN-) gets to take the honey and run (take the honey and run = -ELOPE) (PENELOPE) from the faithful and patient wife who is constantly weaving (PENELOPE in Homer’s The Odyssey is weaving until the return of her husband Odysseus),
13 Free (UNHAMPERED) to harden me up (harden me up) unfairly (= anagram indicator) (harden me up = UNHAMPERED),
14 Place in the dead centre (INTER) of Tangiers emitting gas (‘tangiers’ emitting ‘gas’ = tnier = INTER),
16 Plagiarist (IMITATOR) is not capable of anything original (IMITATOR),
17 The Irishman (EUROPEAN) who is a Union member? (EUROPEAN member of European Union),
19 Ran the (ran the) relay (= anagram indicator) (ran the = TEHRAN) in Asian capital (TEHRAN is capital of Iran)
21 They do nothing (IDLERS) with the loungers (IDLERS),
23 Those runners from The Maze (RATS) caught up (= reverse indicator) in customs tariffs (caught up in ‘customS TARiffs’ = star = RATS),
24 Credit (TICK) for taking hotel (h) from local fool (thick) (‘thick’ without ‘h’ = TICK).