ACROSS
 8. <blackmail material> KOMPROMAT = KO MP + ROT outside MA
10. <rear> RAISE = (.t)RA IS E(u.)
11. <old man not paying> DEADBEAT DAD = £*A DEBT*£
12. I_ C_ E_ = ICE <off>
13. TA KEN = TAKEN <already in a relationship>
14. (THIS MINOR)* = IRONSMITH <forger>
15. <cafeteria> BUTTERY = BY outside UTTER
17. <awful> HEINOUS = HE I_ NOUS
18. AD isnide ROB LOCK = ROADBLOCK <checkpoint>
20. <tree> ASPEN = A SPEN[-t]
22. S out of SALE = ALE <beer>
23. EXTRA _DITION_ = EXTRADITION <delivery abroad>
25. <flower> LOTUS = LOTS outside U
26. <repetitive> REDUNDANT = RANT outside E_D _U_N_D

DOWN
 1. <approved> OKED = K inside OED
 2. <get on board> EMBARK = E _M BARK
 3. IMP + ARITY = IMPARITY <unequal treatment>
 4. <digs> STUDIO = STUD I O
 5. (PESTI_ outside RED) NATION = PREDESTINATION <fate>
 6. <skin condition> VITILIGO = ←IV← TIL I GO
 7. LED (ON SHEER)* = LEDERHOSEN <legwear>
 9. (BIRDERS ARE NOT)* outside B = ROBIN REDBREAST <bird>
13. TAB ERE outside NACL = TABERNACLE <sacred box>
16. TT Y outside RAVE'S = TRAVESTY <burlesque>
17. <Japanese island> HOKKAIDO = H OO outside KK AID
19. [-r]OTTERS = OTTERS <aquatic mammals>
21. PRIM AL = PRIMAL <basic>
24. <memorandum> NOTE = NOT E_