Record's after live electronic sound (4)
I believe the answer is:
beep
'electronic sound' is the definition.
(I've seen this before)
'record's after live' is the wordplay.
'record' becomes 'ep'.
'after' says to put letters next to each other.
'live' becomes 'be' ('be' can be a synonym of 'live').
'ep' put after 'be' is 'BEEP'.
(Other definitions for beep that I've seen before include "Alarming noise" , "Electronic noise" , "Honk" , "Short high-pitched sound from an electronic device" , "Warning signal" .)