Trifling job for a musician (8)
I believe the answer is:
fiddling
'trifling' is the definition.
(thesaurus)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for fiddling that I've seen before include "Cooking the books" , "Tinkering - trifling" , "trivial" , "Such swindles may be" , "petty" .)