Direct channel on the radio (8)
I believe the answer is:
straight
'direct' is the definition.
(I know that direct can be written as straight)
'channel on the radio' is the wordplay.
'channel' becomes 'strait' (strait is a kind of channel).
'on the radio' indicates a 'sounds like' (homophone) clue.
'strait' is a homophone of 'STRAIGHT'.
(Other definitions for straight that I've seen before include "not gay" , "Candid" , "Direct, having no deviations" , "Liking the opposite sex" , "proper place" .)