Reportedly trade mushrooms for guns (6)
I believe the answer is:
biceps
'guns' is the definition.
(I've seen this in another clue)
'reportedly trade mushrooms' is the wordplay.
'reportedly trade' becomes 'bi' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'mushrooms' becomes 'ceps' (cep is a type of mushroom).
'bi'+'ceps'='BICEPS'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for biceps that I've seen before include "Muscle that flexes the forearm" , "Elbow-bending muscle" , "Type of muscle" , "One operating arm" , "Large upper arm muscle" .)