Crossword Genius

Trade that's expensive having changed sides (4)

Ross

I believe the answer is:

deal

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'trade' is the definition.
(synonyms)

I cannot understand how the remainder of the clue works.

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(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" .)

I've seen this clue in The Telegraph.
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