Demand fair exchange (6)
I believe the answer is:
market
I believe this clue is a triple definition!
'demand' is the first definition.
(market can mean commercial demand)
'fair' is the second definition.
(thesaurus)
'exchange' is the third definition.
(thesaurus)
(Other definitions for market that I've seen before include "Commercial location" , "Offer for sale, demand" , "Make commercial" , "Commercial area" , "Where goods and services are bought and sold" .)