Antique coach given to couple — it might represent preferential treatment (3,6,3)
I believe the answer is:
old school tie
'it might represent preferential treatment' is the definition.
The definition suggests a singular noun which matches the answer.
'antique coach given to couple' is the wordplay.
'antique' becomes 'old' (similar in meaning).
'coach' becomes 'school' (both can mean to teach or train).
'given to' is a charade indicator (letters next to each other).
'couple' becomes 'tie' (both can mean to join).
'old'+'school'+'tie'='OLD SCHOOL TIE'
Can you help me to learn more?
(Other definitions for old school tie that I've seen before include "Emblem of a person's education" , "Symbol of private education" , "Perceived social and business network based on education" , "Term for group loyalty of those with posh private eduction" , "Loyalty of those educated together" .)