Chivalrous title (3)
I believe the answer is:
sir
'chivalrous title' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sir that I've seen before include "Noble title of undesirable kind" , "Knight's title" , "Polite form of address to a man" , "Title of knight or baronet" , "Poet and novelist" .)