Smear — slander (8)
I believe the answer is:
besmirch
I believe this clue is a double definition.
'smear' is the first definition.
(I know that smear can be written as besmirch)
'slander' is the second definition.
(I know that slander can be written as besmirch)
(Other definitions for besmirch that I've seen before include "Foul" , "soil" , "Damage (a reputation)" , "run down" , "dull" .)