Sound of distorted dialogue, eg line's split (5)
I believe the answer is:
audio
'sound' is the definition.
('audio' can be a synonym of 'sound')
I can't explain the remainder of the clue.
(Other definitions for audio that I've seen before include "Sound broadcast" , "- - visual aids" , "Relating to sound or hearing" , "Television sound" , "Sound recording" .)