Channel without water mentioned (6)
I believe the answer is:
strait
'channel' is the definition.
(strait is a kind of channel)
'without water mentioned' is the wordplay.
'without water' becomes 'straight' (as in straight whisky).
'mentioned' shows a homophone (sound like).
'straight' sounds like 'STRAIT'.
(Other definitions for strait that I've seen before include "'Bering or Gibraltar, say (6)'" , "Narrow waterway" , "Sound" , "Difficult state for artist" , "Narrow sort of traits (6)" .)