Wagner opera heroine (6)
I believe the answer is:
isolde
'wagner opera heroine' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for isolde that I've seen before include "Soiled like Tristram's medieval lover" , "for Tristram" , "Irish princess" , "King Mark's betrothed (Wagner)" , "heroine (sic)" .)