Become undone (7)
I believe the answer is:
unravel
'become undone' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for unravel that I've seen before include "Make sense of" , "Unpick, untangle" , "Sort out" , "Disentangle knitted wool or solve mystery" , "Undo; begin to collapse" .)