Across:
8 Concerns the people (PUBLIC) in (in) state (= homophone indicator) (‘in’ = ‘inn’ = PUB-) getting brief (k) taste of something (‘lick’ without ‘k’ = -LIC) (PUBLIC),
9 Mad plot (mad plot) organised (= anagram indicator) (mad plot = D-PLOMAT) around one (-I-) (DIPLOMAT) running a mission (DIPLOMAT),
10 Exhibited the effects of time (AGED) consumed by mortgage debt (consumed by ‘mortgAGE Debt’ = AGED).
11 Cake (DANISH) from Down (down/low = BLUE) (DANISH BLUE) served up onboard? (DANISH BLUE served up on cheese board),
12 Holding the top three places (for winners = PODIUM) for opium (opium) production (= anagram indicator) (opium = PO-IUM) around delta (-D-) (PODIUM),
14 Esther edges away (‘e’ + ‘r’) (‘EstheR’ without ‘er’ = STHE-) after (= position indicator) Russell (AE- Russell) finds Lawrence (-TE Lawrence) (AESTHETE) is sensitive to arty types (AESTHETE)
15 They employ those in 22 across (PUBLIC LIBRARIES employ ‘librarians’) and 8 across (‘public’ = PUBLIC) from bookstores? (book stores = LIBRARIES) (PUBLIC LIBRARIES),
18 Sauciest (sauciest) dress (= anagram indicator) (sauciest = SUITCASE) for the holidays (SUITCASE),
20 Director general (DG = D-G-) welcomes the German (‘the’ German = der) back (= reverse indicator) (der = -RED-) from Spain (-E) (DREDGE) to do some work on ocean liner? (to do some work on oceanliner/dredge the bottom = DREDGE),
22 They know where there’s a stack of Bibles (LIBRARIANS) for those having a job stocking shelves (LIBRARIANS),
24 What’s held by one of those in 15 across (BOOK held by ‘public libraries’) in reserve (reserve/hire = BOOK),
25 It relates to ideas and customs (CULTURAL) of sect (CULT-) on Russian river (-URAL) (CULTURAL),
26 Concerns Will (ESTATE) and Earl (E-) from Oklahoma (-STATE) (ESTATE).
Down:
1 Very zealous (GUNG-HO) piece (GUN-) on a fair amount of (half) spirits (ghosts) (a fair amount of ‘GHOsts’ = -G HO) (GUNG-HO),
2 Not upset (GLAD), by and large, dropping Barney (‘by and large’ dropping ‘Barney’ = dlag = GLAD),
3 Account (AC-) on New (= anagram indicator) Media (media = -ADEMI-) caught (-C) (ACADEMIC) by intellectual (ACADEMIC),
4 Carted out of the dead centre (‘carted’ out of the ‘dead centre’ = eden = EDEN) of paradise (EDEN),
5 Resorts (spas = SPAS-) to initiating misery (initiating ‘Misery’ = -M-) on bender (-S bend) (SPASMS) with jerks (SPASMS),
6 Top of the range (HOB-) barbecue on front (‘Barbecue’ on front = -B-) yard (-Y) produced by stud (HORSE) (HOBBY HORSE) with a preoccupation (preoccupation/favourite topic = HOBBY HORSE),
7 Stick produced in France (BAGUETTE) and Belgium (B-E) over lawyer (Attorney General = -AG-) heading off (s) to sue (sue) (‘sue’ without ‘s’ = -UE-) leaders of think tank (leaders of ‘Think Tank’ = -TT-) (BAGUETTE),
13 Unable to read or write (ILLITERATE) from the Italian (‘the’ Italian = IL-) atelier (atelier = -LITERA-E) overlooking square (-T- square) (ILLITERATE),
14 Local chipper (local ‘chipper’ = ALIVE) gets a (A-) vile (vile = evil) review (= reversal indicator) (evil = -LIVE) (ALIVE),
16 Takes a lot of interest (lending at high/extortionate interest rates = USURIOUS) in you and me (us) on both sides (us + us = US-US) of youth centre (‘yoUth’ centre = -U-) riot (riot) endlessly (t) (‘riot’ without ‘t’ = -RIO-) (USURIOUS),
17 Irish race (Irish ‘race’ = rás = RA-S) consuming paella, for instance (-DISH-), from Spain (-E-) (RADISHES) with root vegetables (RADISHES),
19 Praetorian guard takes off, departing (‘praetorian guard’ takes off ‘departing’ = roraua = AURORA) for light show (AURORA),
21 Unpleasant local (GROTTY) teetotaller (-TT-) consumed by wild (= anagram indicator) orgy (orgy = GRO-Y) (GROTTY),
23 Allowed to (ABLE) get around (= reversal indicator) Mediterranean island (Elba = ABLE),
24 Some society ball (some ‘sociETY Ball’ = etyb) recalled (= reverse indicator) (etyb = BYTE) from bit of memory (BYTE).