Slight mumble (4)
I believe the answer is:
slur
This clue is a double definition.
'slight' is the first definition.
(thesaurus)
'mumble' is the second definition.
(thesaurus)
(Other definitions for slur that I've seen before include "Slight - mumble" , "Disparaging remark" , "Speak as drunk perhaps" , "Pronounce indistinctly with each sound running into the next" , "making indistinct sound" .)