Cut a former partner returning (3)
I believe the answer is:
axe
'cut' is the definition.
(both can mean to cancel or remove)
'a former partner returning' is the wordplay.
'former partner' becomes 'ex' (an ex-partner).
'returning' is a reversal indicator.
'ex' back-to-front is 'xe'.
'a'+'xe'='AXE'
(Other definitions for axe that I've seen before include "Fraternize" , "Chop" , "saw alternative?" , "Terminate; chopper" , "fell" .)