Canadian neighbour in Toronto had illness coming back (5)
I believe the answer is:
idaho
'canadian neighbour' is the definition.
(Idaho borders Canada)
'in toronto had illness coming back' is the wordplay.
'in' indicates a hidden word.
'coming back' says the letters should be written backwards.
'ohadi' is hidden in the letters of 'toronto had illness'.
'ohadi' back-to-front is 'IDAHO'.
(Other definitions for idaho that I've seen before include "US state S. of Montana" , "Rocky Mountain state" , "North-western US state" , "US state in the Rocky Mountains" , "North-western state of America" .)