Unexpected defeats (6)
I believe the answer is:
upsets
'unexpected defeats' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for upsets that I've seen before include "Unexpected results" , "Disturbs or knocks over" , "Disapppointments" , "Makes unhappy or worried" , "Disturbs, distresses" .)