Paint I'm mixing in drums (7)
I believe the answer is:
timpani
'drums' is the definition.
(type of drums)
'paint i'm mixing' is the wordplay.
'mixing' is an anagram indicator.
'paint'+'im'='paintim'
'paintim' is an anagram of 'TIMPANI'.
'in' acts as a link.
(Other definitions for timpani that I've seen before include "Those beaten" , "Main pit (anag) - drums" , "orchestra members" , "> kitchen equipment?" , "Mini tap on a large drum" .)