Avoided broadcast channel (4)
I believe the answer is:
duct
'channel' is the definition.
(duct is a kind of channel)
'avoided broadcast' is the wordplay.
'avoided' becomes 'ducked' (ducking is a kind of avoiding).
'broadcast' shows a homophone (sound like) (how the word might sound on the radio or TV).
'ducked' is a homophone of 'DUCT'.
(Other definitions for duct that I've seen before include "Pipe conveying fluid or gas" , "Pipe for cables or air" , "Tube, passageway" , "Tube for cables, air, etc" , "Passage for cables etc." .)