Expressing disapproval, no good disappearing all together (5)
I believe the answer is:
tutti
'all together' is the definition.
(I've seen this before)
'expressing disapproval no good disappearing' is the wordplay.
I cannot really see how this works, but
'disapproval' could be 'tut' (I have seen 'Express disapproval' mean 'tut' so perhaps 'disapproval' could also mean 'tut') and 'tut' is found in the answer.
The remaining letters 'ti' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
(Other definitions for tutti that I've seen before include "(Of an orchestra) all to play together" , "[MUSICIAN] play together" , "Section for all musicians" , "All (stage direction)" , "With all instruments playing at once (music)" .)