Opera about an opera singer (5)
I believe the answer is:
tosca
'opera about an opera singer' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tosca that I've seen before include "Coats off for Pucccni's opera" , "title role" , "Opera - a Scot (anag)" , "musical work" , "Luigi -, Italian playwright" .)