He makes a fair award for one involved in unusual barter (7)
I believe the answer is:
arbiter
'he makes a fair award' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'one involved in unusual barter' is the wordplay.
'one' becomes 'i' (Roman numeral).
'involved in' is an insertion indicator.
'unusual' indicates anagramming the letters.
'barter' anagrammed gives 'arbter'.
'i' placed into 'arbter' is 'ARBITER'.
'for' is the link.
Can you help me to learn more?
(Other definitions for arbiter that I've seen before include "Settler of dispute" , "Rear bit (anag.)" , "One appointed to settle a dispute" , "Decision maker" , "Settler of disputes" .)