Evacuate former spouse onto island (7)
I believe the answer is:
excrete
'evacuate' is the definition.
'former spouse onto island' is the wordplay.
'former spouse' becomes 'ex' (an ex-spouse).
'onto' means one lot of letters go next to another.
'island' becomes 'Crete' (Greek island).
'ex'+'crete'='EXCRETE'
(Other definitions for excrete that I've seen before include "Expel (waste) from the body" , "Defecate" , "Eliminate (from the body)" .)