Representative of a polite chap (5)
I believe the answer is:
agent
'representative' is the definition.
(agent is a kind of representative)
'a polite chap' is the wordplay.
'polite chap' becomes 'gent' (a gentleman).
'a'+'gent'='AGENT'
'of' acts as a link.
(Other definitions for agent that I've seen before include "Business manager" , "One does business on behalf of another" , "Representative - means" , "Actors' manager" , "Middleman" .)