Wrongly rated right businessman (6)
I believe the answer is:
trader
'businessman' is the definition.
(I know that trader is a type of merchant)
'wrongly rated right' is the wordplay.
'wrongly' indicates anagramming the letters (I've seen this in other clues).
'right' becomes 'r' (common abbreviation).
'rated' anagrammed gives 'trade'.
'trade'+'r'='TRADER'
(Other definitions for trader that I've seen before include "He buys and sells goods" , "Dealer, monger" , "One buys and sells" , "Tarred the dealer badly" , "One in business" .)