Opera singer? Not entirely (5)
I believe the answer is:
tenor
'opera singer?' is the definition.
(I've seen this in another clue)
'not entirely' is the wordplay.
I cannot really understand how this works, but
'not' could be 'no' (negative) and 'no' is found in the answer.
The remaining letters 'ter' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tenor that I've seen before include "direction" , "Pavarotti, for example" , "intent" , "Male voice (one of three?)" , "Eg, Placido Domingo" .)