One with negative response wins against a second person, right? (9)
I believe the answer is:
gainsayer
'one with negative response' is the definition.
'wins against a second person right?' is the wordplay.
'wins' becomes 'gains' ('gain' can be a synonym of 'win'**).
'against' is a charade indicator (letters next to each other).
'second person' becomes 'ye' (historical second-person pronoun).
'right?' becomes 'r' (common abbreviation).
'gains'+'a'+'ye'+'r'='GAINSAYER'
(Other definitions for gainsayer that I've seen before include "One contradicting" , "One who contradicts" , "Person who denies" .)