Talk like Daffy Duck (4)
I believe the answer is:
lisp
'talk like daffy duck' 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 "Slip into speech defect" , "peech impediment" , "Slight speech impediment" , "Thpeak like thith" , "Be unable to pronounce S" .)