Outcast from one-time French island (5)
I believe the answer is:
exile
'outcast' is the definition.
(I've seen this in another clue)
'one-time french island' is the wordplay.
'one-time' becomes 'ex' (prefix meaning former or onetime).
'french island' becomes 'ile' ('island' in French).
'ex'+'ile'='EXILE'
'from' is the link.
(Other definitions for exile that I've seen before include "One forced to live abroad" , "Expel from home or country" , "Person forced from country" , "Deportation" , "Banishment from home" .)