Pirates of Penzance heroine (5)
I believe the answer is:
mabel
'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 "Woman" , "Mack's mate" , "Female name; rhymes with mythic story" , "Girl" , "Musical, Mack & --" .)