Daffy Duck's impediment (4)
I believe the answer is:
lisp
'daffy duck's impediment' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lisp that I've seen before include "Be unable to pronounce S" , "peech impediment" , "speak imperfectly" , "Slight speech impediment" , "Talk like thith" .)