Broker (5)
'broker' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for agent that I've seen before include "Person who does business on behalf of another" , "Negotiator" , "Person acting on behalf of another" , "Salesman" , "Traveller" .)
(Other definitions for rep that I've seen before include "Repertory theatre" , "what a draper usually sells" , "agent" , "Sort of theatre" , "Corded fabric" .)