Across:
8 Of sound mind (STABLE) in street (ST-) in 2 down ('able' = -ABLE) (STABLE),
9 Perfect for protecting one’s arms (HOLSTERS) writing (one the 3Rs = -R-) in new (= anagram indicator) hostels (hostels = HOLSTE-S) (HOLSTERS),
10 Part of revolutionary (= reverse indicator) pamphlet – a metaphysical (part of ‘pamphlET A Metaphysical’ = etam = MATE) type that’s one of a pair (MATE),
11 Charlatan (MOUNTEBANK) providing law and order in Canada (Mountie) loses his heart (‘hIs’ heart = -i) (‘mountIe without ‘i’ = MOUNTE-) at The Fringe (fringe/verge = -BANK) (MOUNTEBANK),
12 Christmas, for example (Christmas ISLAND), in Ireland, for instance (ISLAND),
14 Salvages (salvages) settlement (= anagram indicator) (salvages = LAS VEGAS) for those gambling with their capital (LAS VEGAS),
15 A ringer perhaps for big Ben (Big Ben the clock tower) (TIME ON ONE’S HANDS) has a few hours to kill (TIME ON ONE’S HANDS),
18 Friend from The Gaeltacht (‘friend’ from The Gaeltacht = ‘cara’ = C-ARA-) welcomes introduction to handbook (introduction to ‘Handbook’ = -H-) for some nice (Nice/French ‘some’ = -DES) (CHARADES) party game (CHARADES)
20 Joy’s (joys = DREAMS) nightmares! (DREAMS),
22 Mere rhetoric, in a manner of speaking (EMPTY WORDS), from Free (free/not occupied = EMPTY) and The Script (WORDS) (EMPTY WORDS),
24 Most of those at the end of 15 across (most of those at end of ‘time one one’s hands’ = HAND) in a full house? (a full house in poker = HAND),
25 Is not guilty (INNOCENT) of selling drink (INN-) around (-O-) capital (capital/money = -CENT) (INNOCENT),
26 Removing lads from studio flat (removing ‘lads’ from ‘studio flat’ = tuioft = OUTFIT) leads to suit (suit = OUTFIT).
Down:
1 Plagiarises (STEALS) from Ibsen out of beastliness ('Ibsen' out of 'beastliness' = atless = STEALS),
2 Allowed to (ABLE) get around (= reversal indicator) Mediterranean island (Elba = ABLE),
3 British (B-) bird (emu = E-MU-) admits reading (one of the 3Rs = -R-) abridged version (e) of Hamlet (‘Dane’ without ‘e’ = -DAN-) (BERMUDAN) to an islander living in a place known for its disappearances (living in Bermuda Triangle = BERMUDAN),
4 Some characters in courthouse (some characters in ‘courTHOUse’ = THOU) with you long ago (THOU),
5 Group (set = -TES) on mountain (alp) serving up (= reverse indicator) (alp = PLA-) (PLATES) a number of dishes (PLATES),
6 An Arabian companion perhaps (STABLEMATE) from 8 across (‘stable’ = STABLE-) and 10 across (‘mate’ = -MATE) (STABLEMATE),
7 Tends to be under the influence (DRUNKARD) of theologian (Doctor of Divinity = D-D) concealing rush (rush = -RUN-) to build (= anagram indicator) ark (ark = -KAR-) (DRUNKARD),
13 It’s a departure from the norm (ABERRATION) for Lincoln (ABE- Lincoln) getting Republican (-R-) quota (-RATION) (ABERRATION),
14 Teacher’s punishment (LINES) is starting to trend (-IN-) – dividing the foreign (‘the’ foreign = le = L-E-) school (-S) (LINES),
16 In the end (= positional indicator), Clement (clement/merciful = -HUMANE) loses the head (s) with what he heard in confession (‘sin’ without ‘s’ = IN-) (INHUMANE), as it’s diabolical (INHUMANE),
17 Salads and chips, for instance (sides = SIDES-), is what you get addressing Native American (-HOW) (SIDESHOW) event that’s not centre stage (SIDESHOW),
19 Presumably, one expects to find you well (locate ground water/well = DOWSER) – bringing you to the watering hole! (DOWSER),
21 One of The Stones, still standing (MENHIR) in central Germany (central ‘gerMany’ = M-) touring (= anagram indicator) Rhine (Rhine = -ENHIR) (MENHIR),
23 Secretariat holds this (‘secrETARiat’ holds this = etar) back (= reversal indicator) (etar = RATE) from judge (RATE),
24 Rains blow down on (HITS) banks of high voltage circuits (banks of ‘HIgh voltage circuiTS’ = HITS).