A slight incoherence in speech (4)
I believe the answer is:
slur
'a slight' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for slur that I've seen before include "Slight - stain" , "Speak indistinctly, as a drunk might" , "Speak as drunk perhaps" , "making indistinct sound" , "Disparaging remark" .)