You must polish, not oil, cue… it’s what Higgins taught (9)
I believe the answer is:
elocution
'you' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see a link between them that I can't see?
'must polish not oil cue it's what higgins taught' is the wordplay.
'not oil cue' can be anagrammed to 'ELOCUTION'.
But, I'm not sure how this is indicated.
Can you help me to learn more?
(Other definitions for elocution that I've seen before include "The art of speaking expressively and well" , "vocal presentation" , "Art of clear speech" , "Diction" , "first class phrasing?" .)