Is unable to get out of Canton (6)
I believe the answer is:
cannot
'is unable to' is the definition.
(I've seen this before)
'out of canton' is the wordplay.
'out of' is an anagram indicator.
'canton' is an anagram of 'CANNOT'.
'get' is the link.
(Other definitions for cannot that I've seen before include "Canton (anag.)" , "Defeatist's word?" , "Is unable to" , "Is not in a position to" , "Is unabe to" .)