Is of a different city (5)
I believe the answer is:
sofia
'city' is the definition.
(I know that Sofia is a city)
'is of a different' is the wordplay.
'different' is an anagram indicator (letters placed in a different order).
'is'+'of'+'a'='isofa'
'isofa' is an anagram of 'SOFIA'.
(Other definitions for sofia that I've seen before include "Bulgarian city" , "seat of government" , "Foreign city" , "Bulgarian capital" , "capital city" .)