Loosen, as laces (4)
I believe the answer is:
undo
'loosen as laces' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for undo that I've seen before include "Open button or ruin" , "Open buttons or ruin" , "Free from ties, laces, etc" , "Loosen; annul" , "Wreck" .)