Channel close to going on air (6)
I believe the answer is:
gutter
'channel' is the definition.
(I know that gutter is a type of channel)
'close to going on air' is the wordplay.
'close to' indicates one should take the final letters (the close/ending of).
'on air' becomes 'utter' (I can't explain this - if you can you should give a lot more credence to this answer).
The final letter of 'going' is 'g'.
'g'+'utter'='GUTTER'
Can you help me to learn more?
(Other definitions for gutter that I've seen before include "piping?" , "Drainage trough" , "Someone removing contents" , "Channel running along the eaves of a building" , "Where snipe can be found" .)