Unravels (5)
I believe the answer is:
frays
'unravels' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for frays that I've seen before include "gets worn out" , "Shows effect of strain" , "Causes a strain on" , "Becomes worn; skirmishes" , "Strains one's nerves" .)