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' indicates an anagram.
'canton' with letters rearranged gives 'CANNOT'.
'get' acts as a 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" .)