Citizen from old city thorn in one’s side it’s assumed (8)
I believe the answer is:
urbanite
'citizen' is the definition.
Both the answer and definition are singular nouns.
Maybe they are linked in a way I don't understand?
'old city thorn in one's side it's assumed' is the wordplay.
'old city' becomes 'ur' (ancient Sumerian city state).
'thorn in one's side' becomes 'bane' (I've seen this in another clue).
'assumed' is an insertion indicator.
'bane' going around 'it' is 'banite'.
'ur'+'banite'='URBANITE'
'from' is the link.
Can you help me to learn more?
(Another definition for urbanite that I've seen is " Unbear it for city dweller".)