One is on right channel (4)
I believe the answer is:
race
'channel' is the definition.
(race is a kind of channel)
'one is on right' is the wordplay.
'one' becomes 'ace' ('ace' can be a synonym of 'one').
'is on' means one lot of letters go next to another.
'right' becomes 'r' (common abbreviation).
'ace' after 'r' is 'RACE'.
(Other definitions for race that I've seen before include "Career - people" , "Participate in speed contest" , "The ... is not to the swift (Bible)" , "Stock" , "Run fast" .)