Former spouse to lie about expatriate (5)
I believe the answer is:
exile
'expatriate' is the definition.
(I know that expatriate can be written as exile)
'former spouse to lie about' is the wordplay.
'former spouse' becomes 'ex' (an ex-spouse).
'about' is an anagram indicator.
'lie' is an anagram of 'ile'.
'ex'+'ile'='EXILE'
(Other definitions for exile that I've seen before include "Deportation" , "Expulsion from one's country" , "Person forced from country" , "Banish from one's country" , "Expel from home or country" .)