Channel immediately being broadcast (6)
I believe the answer is:
strait
'channel' is the definition.
(I know that strait is a type of channel)
'immediately being broadcast' is the wordplay.
'immediately' becomes 'straight' (as in straight away).
'being broadcast' indicates a 'sounds like' (homophone) clue (how the word might sound on the radio or TV).
'straight' sounds like 'STRAIT'.
(Other definitions for strait that I've seen before include "of Gibraltar, for example" , "Narrow stretch of water for artist" , "'Bering or Gibraltar, say (6)'" , "Connecting passage of water" , "-- -laced (prudish)" .)