Paint I'm mixing for instruments (7)
I believe the answer is:
timpani
'instruments' is the definition.
(I've seen this before)
'paint i'm mixing' is the wordplay.
'mixing' indicates anagramming the letters.
'paint'+'im'='paintim'
'paintim' is an anagram of 'TIMPANI'.
'for' is the link.
(Other definitions for timpani that I've seen before include "Mini tap on a large drum" , "Those beaten" , "Tina Pim has a set of kettle drums" , "Percussion section" , "Something making drumming noise" .)