Reportedly film channel (5)
I believe the answer is:
chute
'channel' is the definition.
(chute is a kind of channel)
'reportedly film' is the wordplay.
'reportedly' shows a homophone (sound like).
'film' becomes 'shoot' ('shoot' can be a synonym of 'film').
'shoot' is a homophone of 'CHUTE'.
(Other definitions for chute that I've seen before include "Slide" , "Flume" , "Waterfall" , "Inclined channel for rubbish, laundry etc" , "Sloping trough" .)