Tied in a knot. (That's 'correct') (4)
I believe the answer is:
edit
'correct' is the definition.
(thesaurus)
'tied in a knot' is the wordplay.
'in a knot' indicates an anagram.
'tied' anagrammed gives 'EDIT'.
'that's' is the link.
(Other definitions for edit that I've seen before include "This is an act of cleaning" , "Tide (anag.)" , "Be in charge of (newspaper)" , "Make textual changes" , "Supervise the publication of" .)