It's sharp and injured the girl (7)
I believe the answer is:
cutlass
'it's sharp' is the definition.
I can't tell whether this defines the answer.
'injured the girl' is the wordplay.
'injured' becomes 'cut' (similar in meaning).
'the girl' becomes 'lass' (lass can informally mean a girl).
'cut'+'lass'='CUTLASS'
'and' is the link.
Can you help me to learn more?
(Other definitions for cutlass that I've seen before include "Short curved naval sword" , "Short, broad-bladed sword" , "Sword formerly used by sailors" , "Curved sailors' sword" , "Sailor's blade" .)