Speak indistinctly (6)
'speak indistinctly' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for slur that I've seen before include "Discredit to one's reputation" , "Slight lack of distinction in speech" , "Discredit, say reputation" , "Defamation" , "Disparaging remark" .)
'speak indistinctly' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for mutter that I've seen before include "Talk indistinctly in a low voice - a German mother" , "Speak quietly and indistinctly" , "Grumble under one's breath" , "Barely audible utterance" , "carp, > grouse and > beef" .)