Drain with no cover that carries water (4)
I believe the answer is:
ewer
'that carries water' is the definition.
(type of container for water)
'drain with no cover' is the wordplay.
I cannot really understand how this works, but
'with' could be 'w' (abbreviation) and 'w' is found in the answer.
The remaining letters 'eer' 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 ewer that I've seen before include "Were (anag)" , "29 [VESSEL]" , "Large water-jug" , "Vessel for pouring" , "A wide-lipped jug" .)