A weapon to wound a girl (7)
I believe the answer is:
cutlass
'a weapon' is the definition.
(cutlass is a kind of weapon)
'wound a girl' is the wordplay.
'wound' becomes 'cut' (cut is a kind of wound).
'a girl' becomes 'lass' (lass can informally mean a girl).
'cut'+'lass'='CUTLASS'
'to' acts as a link.
(Other definitions for cutlass that I've seen before include "Type of sword" , "Curved, one-edged sword" , "Short curved naval sword" , "Short, heavy curved sword" , "Old sailor's weapon" .)