Just a trade exhibition (4)
I believe the answer is:
fair
This clue is a triple definition!
'just' is the first definition.
(just can mean fair in the sense of showing justice)
'a trade' is the second definition.
(thesaurus)
'exhibition' is the third definition.
(fair is a kind of exhibition)
(Other definitions for fair that I've seen before include "Free from bias" , "Traders' gathering" , "Market for the sale of produce" , "Blonde; impartial" , "Beautiful like maiden of old" .)