Former spouse sat in the open (7)
I believe the answer is:
exposed
'in the open' is the definition.
(I've seen this in another clue)
'former spouse sat' is the wordplay.
'former spouse' becomes 'ex' (an ex-spouse).
'sat' becomes 'posed' ('pose' can be a synonym of 'sit').
'ex'+'posed'='EXPOSED'
(Other definitions for exposed that I've seen before include "vulnerable" , "Without protection" , "Made known" , "in the nude" , "Made public" .)