Injured leader departs, carrying a weapon (5)
I believe the answer is:
armed
'carrying a weapon' is the definition.
(I've seen this in another clue)
'injured leader departs' is the wordplay.
'injured' becomes 'harmed' (harming is a kind of injuring).
'leader departs' means to remove the first letter (I've seen 'leader departing' mean this).
'harmed' with its initial letter removed is 'ARMED'.
(Other definitions for armed that I've seen before include "Dream about carrying weapons" , "Given weapons" , "Gave weapon" , "ready for exchange?" , "Having guns" .)