Maine's not to be confused with this state (9)
I believe the answer is:
minnesota
'this state' is the definition.
(US state)
'maine's not to be confused' is the wordplay.
'to be confused' indicates an anagram.
'maines'+'not'='mainesnot'
'mainesnot' anagrammed gives 'MINNESOTA'.
'with' acts as a link.
(Other definitions for minnesota that I've seen before include "US state -. of Iowa" , "Wobegon state (Keillor)" , "Nominates, oddly, the US state" , "American state, capital St Paul" , "Nominates the strange state" .)