Former spouse to lie about expulsion (5)
I believe the answer is:
exile
'expulsion' is the definition.
(thesaurus)
'former spouse to lie about' is the wordplay.
'former spouse' becomes 'ex' (an ex-spouse).
'about' indicates anagramming the letters.
'lie' with letters rearranged gives 'ile'.
'ex'+'ile'='EXILE'
(Other definitions for exile that I've seen before include "Banish from one's country" , "Overseas banishment" , "Ousted person" , "Drive away" , "Send abroad as punishment" .)