Carried over, being unwanted (2,4)
I believe the answer is:
de trop
'unwanted' is the definition.
('de trop' can be similar in meaning to 'unwanted')
'carried over' is the wordplay.
'carried' becomes 'ported' (porting is a kind of carrying).
'over' shows that the letters should be reversed in order.
'ported' reversed gives 'DE TROP'.
'being' acts as a link.
(Other definitions for de trop that I've seen before include "In the way, unwanted as in France" , "Superfluous (French)" , "Deport from France, being in the way?" , "'Unreasonable or unwelcome (2,4)'" , "Unnecessary" .)