Trade that's expensive having changed sides (4)
I believe the answer is:
deal
'trade' is the definition.
(synonyms)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for deal that I've seen before include "A port, a bargain" , "Hand out playing cards" , "Business transaction of timber." , "Bargain, contract" , "Share out (cards); wood" .)