Free former partner roughly in common (9)
I believe the answer is:
extricate
'free' is the definition.
(extricating is a kind of freeing)
'former partner roughly in common' is the wordplay.
'former partner' becomes 'ex' (an ex-partner).
'roughly' becomes 'ca' (abbreviation for circa).
'in' indicates putting letters inside.
'common' becomes 'trite' (trite can mean common or cliched).
'ca' placed inside 'trite' is 'tricate'.
'ex'+'tricate'='EXTRICATE'
(Other definitions for extricate that I've seen before include "Free from complicated situation" , "Free (something) from difficulty" , "Disentangle, set free" , "Get free from" , "get out from difficult situation" .)