Channel without water we hear (6)
I believe the answer is:
strait
'channel' is the definition.
(I know that strait is a type of channel)
'without water we hear' is the wordplay.
'without water' becomes 'straight' (as in straight whisky).
'we hear' shows a homophone (sound like).
'straight' sounds like 'STRAIT'.
(Other definitions for strait that I've seen before include "Narrow kind of traits" , "Narrow passage joining two large areas of water" , "Narrow strip of water between two larger ones" , "Narrow watery stretch" , "watery scene?" .)