Smooth self-confidence about one in the city (3,5)
I believe the answer is:
san diego
'city' is the definition.
(San Diego is an example)
'smooth self-confidence about one' is the wordplay.
'smooth' becomes 'sand' (sanding is a kind of smoothing**).
'self confidence' becomes 'ego'.
'about' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'ego' after 'i' is 'iego'.
'sand'+'iego'='SAN DIEGO'
'in the' acts as a link.
(Other definitions for san diego that I've seen before include "Agonised over the Californian city" , "Calif. naval base" , "US city" , "California naval port" , "Southern California naval base" .)