Perform with former wife and sweetheart? Sweet! (7)
I believe the answer is:
execute
'perform' is the definition.
('execute' can be a synonym of 'perform')
'former wife and sweetheart? sweet' is the wordplay.
'former wife' becomes 'ex'.
'and' means one lot of letters go next to another.
'sweetheart?' becomes 'e' (the heart/centre of 'sweet').
'sweet' becomes 'cute' (I've seen this before).
'ex'+'e'+'cute'='EXECUTE'
'with' acts as a link.
(Other definitions for execute that I've seen before include "Discharge" , "run a program" , "Put (plan) into effect; kill (a condemned person)" , "Get it done" , "ice" .)