Smart work outside a US city (7)
I believe the answer is:
chicago
'us city' is the definition.
(Chicago is a US city)
'smart work outside a' is the wordplay.
'smart' becomes 'chic' (both can mean stylish).
'work' becomes 'go' (synonyms).
'outside' is an insertion indicator (some letters go outside others).
'chic'+'go'='chicgo'
'chicgo' enclosing 'a' is 'CHICAGO'.
(Other definitions for chicago that I've seen before include "Illinois port" , "1970s' John Kander/Fred Ebb musical" , "Windy City of USA" , "Type of bridge" , "City on Lake Michigan" .)