Apathy Sketchpad

Here is a puzzle I have invented. Solve it.

Clues

1. Something odd — dessert begins before a drink. (4)
2. Charged particles — Si? (4)
3. Hitchhiker confused after 4 suggested (6)
4. Heard jolly greeting (2)
5. Heard a relative bet (4)
6. Swindled by headless chad (3)
7. Loathe jumbled articles (4)
8. One bit, say, where a drill might be kept (2,1,4)
9. Cotton’s starting deteriorating on the spindle (4)
10. Endless money for me! (3)
11. After end of bombs, Mandy’s innards found in bunker (4)
12. Warm, with expanded belly. Good times. (4)
13. Walking trees in advent setting (4)
14. Part of the mind has nothing in it (5)
15. Infidel to heartlessly attempt robbery (7)
16. Fuss after a party (3)
17. Polish singer in function (5)
18. Constant singer (1)
19. Mixed side on a plate (7)

This is a Killer Su Doku. It’s a perfectly ordinary Killer Su Doku, except for one minor difference.

I’m sure you’ll work out what it is.