Firm with former spouse - first live together (7)
I believe the answer is:
coexist
'live together' is the definition.
(I've seen this before)
'firm with former spouse first' is the wordplay.
'firm' becomes 'co' (a firm is a company).
'with' is a charade indicator (letters next to each other).
'former spouse' becomes 'ex' (an ex-spouse).
'first' becomes 'ist' (ist resembles 1st).
'co'+'ex'+'ist'='COEXIST'
(Other definitions for coexist that I've seen before include "Live together peacefully" , "Get along together" , "Live side by side" , "Avoid conflict" , "Live together in peace" .)