Improve on the ebb tide (4)
I believe the answer is:
edit
'improve' is the definition.
(thesaurus)
'the ebb tide' is the wordplay.
'the ebb' shows that the letters should be reversed in order (I've seen 'ebbing' mean this (to ebb can mean to go backwards)).
'tide' back-to-front is 'EDIT'.
'on' acts as a link.
(Other definitions for edit that I've seen before include "Literally, arrange" , "Amend text" , "Rewrite" , "Prepare text for publication" , "Redact, perhaps" .)