Weapon injured girl (7)
I believe the answer is:
cutlass
'weapon' is the definition.
(cutlass is a kind of weapon)
'injured girl' is the wordplay.
'injured' becomes 'cut' (similar in meaning).
'girl' becomes 'lass' (lass can informally mean a girl).
'cut'+'lass'='CUTLASS'
(Other definitions for cutlass that I've seen before include "Sharp weapon" , "What Blackbeard wielded" , "Curved, one-edged sword" , "Short, heavy curved sword" , "Sword formerly used by sailors" .)