North American province, not a different South American city (7)
I believe the answer is:
ontario
'north american province' is the definition.
(province of Canada)
'not a different south american city' is the wordplay.
'different' is an anagram indicator.
'south american city' becomes 'rio' (I've seen this before).
'not'+'a'='nota'
'nota' anagrammed gives 'onta'.
'onta'+'rio'='ONTARIO'
(Other definitions for ontario that I've seen before include "vast lake" , "Province of SE Canada, and a Great Lake" , "Most easterly Great Lake" , "Smallest of the Great Lakes" , "One of the Great Lakes" .)