Turkish honorific (3)
I believe the answer is:
'turkish honorific' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for aga that I've seen before include "military leader" , "Type of stove" , "Palindromic Turkish commander" , "Muslim title of honour" , "--- Khan, title of the head of the Ismaili Muslims" .)