Passage of moving water (7)
I believe the answer is:
tideway
'water' is the definition.
(I know that tideway is a type of channel)
'passage of moving' is the wordplay.
I cannot quite understand how this works, but
'passage' could be 'way' (I've seen this in other clues) and 'way' is found in the answer.
The remaining letters 'tide' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tideway that I've seen before include "River channel at sea level" , "Part of river affected by ebb and flow of the sea" , "Seaward part of river" , "current track" , "Channel with ebb and flow" .)