Actor's representation of a well-mannered person (5)
I believe the answer is:
agent
'actor's representation' is the definition.
(someone representing an actor professionally)
'a well-mannered person' is the wordplay.
'well-mannered person' becomes 'gent' (gentleman).
'a'+'gent'='AGENT'
'of' is the link.
(Other definitions for agent that I've seen before include "Spy; service provider" , "Double-zero-seven, for example" , "Factor, spy" , "One representing others" , "One's representative" .)