Stop girl getting an instrument (5)
I believe the answer is:
banjo
'an instrument' is the definition.
(I know that banjo is a type of stringed instrument)
'stop girl getting' is the wordplay.
'stop' becomes 'ban' (I've seen this in another clue).
'girl' becomes 'jo' (woman's name).
'getting' is a charade indicator (letters next to each other).
'ban'+'jo'='BANJO'
(Other definitions for banjo that I've seen before include "Formby's instrument" , "Stringed instrument beloved of old minstrel shows" , "Stringed instrument with long neck" , "something that's played on" , "Guitar-like instrument" .)