Narrowly defeat English on channel (4)
I believe the answer is:
pipe
'channel' is the definition.
(pipe is a kind of channel)
'narrowly defeat english on' is the wordplay.
'narrowly defeat' becomes 'pip' (I've seen this before).
'english' becomes 'e' (abbreviation).
'on' says to put letters next to each other.
'pip'+'e'='PIPE'
(Other definitions for pipe that I've seen before include "Wine cask; sing shrilly" , "Long tube" , "Tube, maybe musical" , "Smoker's item" , "Tobacco is smoked in it" .)