City worker rejected socialist realism, say (6)
I believe the answer is:
trader
'city worker' is the definition.
'rejected socialist realism say' is the wordplay.
'rejected' says the letters should be written in reverse.
'socialist' becomes 'red' (red is a kind of socialist).
'realism say' becomes 'art' (realism is a kind of art).
'red'+'art'='redart'
'redart' written backwards gives 'TRADER'.
(Other definitions for trader that I've seen before include "Retard (anag.)" , "One buys and sells" , "Person in the business of buying and selling" , "One in business" , "Dealer who buys and sells" .)