Friend holds revolutionary knife (7)
I believe the answer is:
machete
'knife' is the definition.
(machete is a kind of knife)
'friend holds revolutionary' is the wordplay.
'friend' becomes 'mate' (mate is a kind of friend**).
'holds' indicates putting letters inside.
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'mate' going around 'che' is 'MACHETE'.
(Other definitions for machete that I've seen before include "A heavy-duty jungle knife" , "Teach me with large jungle knife" , "Heavy knife used as weapon" , "hacker" , "Broad heavy knife used in S American jungles" .)