Decide to go round a US city (7)
I believe the answer is:
seattle
'us city' is the definition.
(city in Washington, USA)
'decide to go round a' is the wordplay.
'decide' becomes 'settle' (synonyms).
'to go round' means one lot of letters goes inside another.
'settle' going around 'a' is 'SEATTLE'.
(Other definitions for seattle that I've seen before include "US West coast port" , "major US port" , "Port of north-west USA" , "somewhere in Washington" , "? American seaport" .)