ACROSS
 1. O + BLAST = OBLAST <somewhere in Bulgaria>
 5. EX PORTER = EXPORTER <one ships abroad>
 9. ←NOB← HOMIE = BONHOMIE <friendliness>
10. <excellent> SUPERB = SUP _ERB_
11. <author> DOROTHY SAYERS = DO SHORTER* outside Y SAY
12. (BELLE outside W) THE R = BELLWETHER <trendsetter>
15. _I_ RAN = IRAN <country>
16. G HEE[-d] = GHEE <clarified matter>
18. SUN THING outside BA = SUNBATHING <holiday activity>
20. (SEB + URGE) inside CHEERS = CHEESEBURGERS <fast food>
23. <primate> BABOON = B + A BOON
24. <ship sides> GUNWALES = G_ U_ N_ + WALES
25. <student> HEAD GIRL = (HID LAGER)*
26. <tournaments maybe> EVENTS = E VENTS

DOWN
 2. BOND IE outside L = BLONDIE <cake>
 3. <despise> ABHOR = ABH + OR
 4. <alluring woman> = T_ EMPRESS outside T
 5. (NIGHTLY BEVERAGE)* = EVERYTHING BAGEL <bread>
 6. PAST A_ = PASTA = <Italian food>
 7. <top up> = (PILSNER HE)*
 8. ←A IS A RUE← = EURASIA <landmass>
13. <feudal master> LIEGE LORD = LIE GEL O_ R_ D_
14. <change organisation of> REARRANGE = REAR RANGE
17. <unit of area> HECTARE = (THE ACRE)*
19. <beginning> NASCENT = _N ASCENT
21. <religious person> SUNNI = (.t)SUN NI(c.)
22. <cheer> ELATE = EE outside _LAT_