Theme Word.

16ac tells you how to solve the other across clues. (Down clues are normal).

Across:
1. Intestinal contents of bile, alas (4)
3. Great fun absorbs student, though debilitating (8)
9. Gas carver (5)
10. Clobbers wild press-up (7)
11. Rum info, confusing and hook-shaped (7)
13. Wood strip used as door-catch (4)
15. Thrash a sea creature (3)
16. Nearby bar (theme word) (5)
17. Health resort prevents cruelty to animals (3)
18. Idiot has the sulks (4)
20. Drunken individual from north of the border (7)
22. Open and shut (7)
24. Girl, often black (5)
25. Uneasy, lacking comb (8)
26. They help in digestion it's said falsely (4)

Down:
1. Angrily I umpire gully with nog (8)
2. Onomatopoeia from disturbed home (sic) (7)
4. Waifs and strays hide uncertainties (3)
5. Myopic pallet-maker does wart removals (12)
6. Take a shine to exercise, nosh and bungling (5)
7. Effusive display of affection in bogus howl (4)
8. Ectopic april flurry for front of back of head (12)
12. Secures boggy lands (5)
14. Saw, heard, and destroyed explosives (8)
17. Hard carcinomas for Sir mingling with rich (7)
19. We show hesitation with singular employers (5)
21. Yes, our combination belongs to you (4)
23. You saint! You agree! (3)