Injured part of leg in battle (7,4)
I believe the answer is:
wounded knee
'battle' is the definition.
(Battle of Wounded Knee of 1890)
'injured part of leg' is the wordplay.
'injured' becomes 'wounded' (similar in meaning).
'part of leg' becomes 'knee' ('knee' is part of 'leg').
'wounded'+'knee'='WOUNDED KNEE'
'in' acts as a link.
(Other definitions for wounded knee that I've seen before include "associated with massacre" , "historic US location" .)