Yes, right, guv! (3)
I believe the answer is:
sir
'guv' is the definition.
Both the definition and answer are singular nouns.
Maybe there's a link between them I don't understand?
'yes right' is the wordplay.
'yes' becomes 'si' (I can't explain this - if you can you should give a lot more credence to this answer).
'right' becomes 'r' (abbreviation).
'si'+'r'='SIR'
Can you help me to learn more?
(Other definitions for sir that I've seen before include "Gentleman's form of address" , "Title given to baronet" , "Term of address for a gentleman" , "Formal term of address" , "Honourable title" .)