Well-mannered guy (4)
I believe the answer is:
gent
'well-mannered guy' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gent that I've seen before include "Man of good standing (informal)" , "Honourable man" , "bloke" , "Refined man (colloquial)" , "Informal and short man" .)