Bug-hitting-the-windshield sound (5)
I believe the answer is:
splat
'bug-hitting-the-windshield sound' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for splat that I've seen before include "Piece of wood in a chair back" , "Noise of soft wet impact; part of a chair back" , "amusing noise" , "Noise on landing" , "Wet slapping sound" .)