Confidentially, pop music often is (3,3,6)
I believe the answer is:
off the record
'confidentially' is the definition.
(synonyms)
'pop music often is' is the wordplay.
I cannot really understand how this works, but
'music' could be 'f' and 'f' is found in the answer.
'often' could be 'oft' (synonyms) and 'oft' is located in the leftover letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for off the record that I've seen before include "In confidence" , "Deleted from disc" , "in a minute? No" , "Where a needle used be taken" , "not to be broadcast" .)