Operatic heroine is historic, not new (6)
I believe the answer is:
isolde
'operatic heroine' is the definition.
(as in Wagner's Tristan und Isolde)
'is historic not new' is the wordplay.
'historic' becomes 'old' (historic can mean very old).
'not new' becomes 'e' (I can't explain this - if you can you should believe this answer much more).
'is'+'old'+'e'='ISOLDE'
Can you help me to learn more?
(Other definitions for isolde that I've seen before include "Legendary lover" , "Irish princess" , "Soiled like Tristan's lover" , "Soiled like Tristram's girl friend" , "Tristan's lover, sadly soiled" .)