Operatic heroine, and not mother! (5)
I believe the answer is:
norma
'operatic heroine' is the definition.
(I've seen this before)
'and not mother' is the wordplay.
'and not' becomes 'nor' (I've seen this before).
'mother' becomes 'ma' (ma is a kind of mother).
'nor'+'ma'='NORMA'
(Other definitions for norma that I've seen before include "Shearer or Major" , "Female" , "Operatic heroine" , "Marilyn was properly one" , "Girl" .)