Failure - to get rid of with water (7)
I believe the answer is:
washout
'failure' is the definition.
(washout is a kind of failure)
'to get rid of with water' is the wordplay.
I cannot really see how this works, but
'of' could be 'o' and 'o' is present in the answer.
'to' could be 'shut' (I've seen this before) and 'shut' is found within the leftover letters.
'with' could be 'w' (short for with) and 'w' is found within the answer.
A single letter 'a' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for washout that I've seen before include "A complete failure - too much rain" , "match abandoned due to rain?" , "Failure - cancellation" , "Flush" , "Cancelled test, for example" .)