Operatic heroine caught leading man taking off (9)
I believe the answer is:
mimicking
'taking off' is the definition.
(take off can mean to imitate)
'operatic heroine caught leading man' is the wordplay.
'operatic heroine' becomes 'mimi'.
'leading' indicates taking the first letters.
'man' becomes 'king' (king is a kind of man).
The first letter of 'caught' is 'c'.
'mimi'+'c'+'king'='MIMICKING'
(Other definitions for mimicking that I've seen before include "Impersonating" , "Acting like" .)