Food for trader (9)
I believe the answer is:
provender
'food' is the definition.
(provender is a kind of food)
'for trader' is the wordplay.
'for' becomes 'pro' (I've seen this before).
'trader' becomes 'vender'.
'pro'+'vender'='PROVENDER'
(Other definitions for provender that I've seen before include "Animal fodder" , "animal feed" , "Dry food for beasts" , "Dry feed" .)