"The Pirates of Penzance" heroine (5)
I believe the answer is:
mabel
'the pirates of penzance heroine' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for mabel that I've seen before include "Female name deriving from one meaning lovable" , "Lady" , "Musical, Mack & --" , "Blame (anag.), lady's name" , "Woman" .)