Runs out of water (4)
I believe the answer is:
ebbs
'runs' is the definition.
The answer and definition can be both related to natural events as well as being plural nouns.
Maybe there's a link between them I don't understand?
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for ebbs that I've seen before include "flags" , "Goes out like tide" , "Wanes" , "Flows back - declines" , "Declines gradually" .)