Speak unclearly (4)
I believe the answer is:
slur
'speak unclearly' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for slur that I've seen before include "Pronounce words indistinctly" , "disgrace" , "making indistinct sound" , "Negative comment" , "Insinuation, allegation" .)