Smart attempt to circle a US city (7)
I believe the answer is:
chicago
'us city' is the definition.
(Chicago is a US city)
'smart attempt to circle a' is the wordplay.
'smart' becomes 'chic' (both can mean stylish).
'attempt' becomes 'go' (go is a kind of attempt).
'to circle' means one lot of letters goes inside another.
'chic'+'go'='chicgo'
'chicgo' placed around 'a' is 'CHICAGO'.
(Other definitions for chicago that I've seen before include "America's Windy City" , "City on Lake Michigan" , "Type of bridge" , "Musical (in Illinois?)" , "Al Capone's city" .)