Aspersion (4)
I believe the answer is:
slur
'aspersion' is the definition.
(I know that aspersion can be written as slur)
This is the entire clue.
(Other definitions for slur that I've seen before include "Slight - incoherence in speech" , "making indistinct sound" , "Disparage" , "Negative comment" , "Slight - drawl" .)