Make a knot not? (5)
I believe the answer is:
untie
'make a knot not?' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for untie that I've seen before include "Release from bonds or open shoelace" , "Disconnect; release" , "get rid of bonds" , "Undo, unfasten" , "Set free" .)