Correct trend upward (4)
I believe the answer is:
edit
'correct' is the definition.
(thesaurus)
'trend upward' is the wordplay.
'trend' becomes 'tide' (I've seen this before).
'upward' is a reversal indicator.
'tide' in reverse letter order is 'EDIT'.
(Other definitions for edit that I've seen before include "Redact, perhaps" , "Supervise the publication of" , "be a bookmaker" , "Rework (text)" , "Make changes to (text)" .)