Channel avoided on the radio (4)
I believe the answer is:
duct
'channel' is the definition.
(duct is a kind of channel)
'avoided on the radio' is the wordplay.
'avoided' becomes 'ducked' (ducking is a kind of avoiding).
'on the radio' shows a homophone (sound like).
'ducked' is a homophone of 'DUCT'.
(Other definitions for duct that I've seen before include "Passage for cables etc." , "The Eve of St - is a narrative poem by Keats" , "Tube for conveing cable, liquid etc" , "Air passage" , "Tube, passageway" .)