Shoelace snarl (4)
I believe the answer is:
'shoelace snarl' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for knot that I've seen before include "that's sometimes in wood" , "Small northern sandpiper" , "See 2" , "Tie; group" , "Tie; sandpiper" .)