Cultivated fellow leaves with a gun (5)
I believe the answer is:
armed
'with a gun' is the definition.
(armed with a gun)
'cultivated fellow leaves' is the wordplay.
'cultivated' becomes 'farmed' (farming is a kind of cultivating).
'fellow' becomes 'f' (abbreviation - of a society etc.).
'leaves' is a deletion indicator.
'farmed' with 'f' removed is 'ARMED'.
(Other definitions for armed that I've seen before include "unlike the Venus of Milo" , "Dream about carrying weapons" , "Carrying a weapon" , "Provided with weapons" , "Prepared and equipped for a confrontation" .)