Articulate doctor checks shopper (9)
I believe the answer is:
denouncer
'shopper' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's an association between them I don't understand?
'articulate doctor checks' is the wordplay.
'articulate' becomes 'enounce' (synonyms).
'doctor' becomes 'Dr' (abbreviation).
'checks' means one lot of letters goes inside another (inserted letters are checked or controlled).
'enounce' inserted within 'dr' is 'DENOUNCER'.
Can you help me to learn more?
(Other definitions for denouncer that I've seen before include "One making a public accusation" , "Castigator" , "One condemns" , "Informer against" .)