End of broadcasting, say, for channel (6)
I believe the answer is:
gutter
'for channel' is the definition.
(gutter is a kind of channel)
'end of broadcasting say' is the wordplay.
'end of' suggests the final letters.
'say' becomes 'utter' (to utter something is to speak or say it).
The final letter of 'broadcasting' is 'g'.
'g'+'utter'='GUTTER'
(Other definitions for gutter that I've seen before include "Channel running along the eaves of a building" , "Threaten to go out" , "piping?" , "Drainage trough" , "Street channel for carrying off rainwater" .)