Goes out, as the tide (4)
I believe the answer is:
ebbs
'goes out as the tide' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ebbs that I've seen before include "Flows back or recedes" , "Flows back - declines" , "Declines gradually" , "flags" , "Subsides" .)