This has taken me far too long & I'm defeated by three clues;
16 dn Look into WW1 aircraft to find chemical cleanse (7) c?l?m??
17dn Down a mine covering money up, they're beaten (7) t?m?a?? Could be timpani but can't parse..
23 ac No separating us if my rival's come clean! (5,4,2)
l???????h?e
Many Thanks in advance..