Channel showing 'Midnight Express' (6)
I believe the answer is:
gutter
'channel' is the definition.
(gutter is a kind of channel)
'midnight express' is the wordplay.
'midnight' becomes 'g' (**).
'express' becomes 'utter' ('utter' can be a synonym of 'express').
'g'+'utter'='GUTTER'
'showing' acts as a link.
(Other definitions for gutter that I've seen before include "Someone removing contents" , "Threaten to go out" , "piping?" , "Drainage trough" , "Channel at the side of a street" .)