In with winner vying, on edge (5)
I believe the answer is:
nervy
'on edge' is the definition.
(I've seen this before)
'in with winner vying' is the wordplay.
'in' indicates a hidden word.
'NERVY' is hidden in the letters of 'with winner vying'.
(Other definitions for nervy that I've seen before include "Fidgety" , "Highly-strung" , "Anxious, jumpy" , "Strained" , "Highly strung" .)