Record is after live electronic sound (4)
I believe the answer is:
beep
'electronic sound' is the definition.
(I've seen this before)
'record is after live' is the wordplay.
'record' becomes 'EP' (abbreviation for extended play record).
'is after' says to put letters next to each other.
'live' becomes 'be' (synonyms).
'ep' put after 'be' is 'BEEP'.
(Other definitions for beep that I've seen before include "Electronic noise" , "Toot" , "Honk" , "Alarming noise" , "Sound of pager" .)