Electronic sound in missable episode (5)
I believe the answer is:
bleep
'electronic sound' is the definition.
(I've seen this before)
'in missable episode' is the wordplay.
'in' indicates the answer is hidden within the clue.
'BLEEP' can be found hidden inside 'missable episode'.
(Other definitions for bleep that I've seen before include "Electronic signal calling a person" , "Electronic sound (used over profanities)" , "High pitched signal" , "Censor" , "Swearing substitute" .)