Surprising result, winning series (5)
I believe the answer is:
upset
'surprising result' is the definition.
(I've seen this before)
'winning series' is the wordplay.
'winning' becomes 'up' (I've seen this in other clues).
'series' becomes 'set' (I've seen this before**).
'up'+'set'='UPSET'
(Other definitions for upset that I've seen before include "Disturb, physically or emotionally" , "Unexpected result" , "Overturn; distress" , "Overturn - perturbed - disordered" , "Overturn, disturb" .)