Shakespearean heroine losing a musical instrument (4)
I believe the answer is:
viol
'musical instrument' is the definition.
(I know that viol is a type of bowed stringed instrument)
'shakespearean heroine losing a' is the wordplay.
'shakespearean heroine' becomes 'viola' (heroine of Shakespeare's Twelfth Night).
'losing' is a deletion indicator.
'viola' with 'a' taken away is 'VIOL'.
(Other definitions for viol that I've seen before include "Old string instrument" , "Old stringed instrument" , "Old consort instrument" , "something from the past to play" , "Early string instrument" .)