Come undone (7)
I believe the answer is:
unravel
'come undone' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for unravel that I've seen before include "Disentangle or undo like knitted fabric" , "Solve the problem" , "Sort out" , "Unpick, untangle" , "Come undone; solve" .)