Canada's ratable system (7)
I believe the answer is:
alberta
'canada's' is the definition.
The definition and answer can be both locations as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'ratable system' is the wordplay.
'system' is an anagram indicator (another version or system with the same letters).
'ratable' with letters rearranged gives 'ALBERTA'.
Can you help me to learn more?
(Other definitions for alberta that I've seen before include "Banff province" , "Canadian province, capital Edmonton" , "region of North America" , "Province of W. Canada" , "Where is Jasper" .)