Debates (6)
I believe the answer is:
argues
'debates' is the definition.
('argue' can be a synonym of 'debate')
This is all the clue.
(Other definitions for argues that I've seen before include "Disputes, expresses disagreement" , "Disputes, proposes the contrary" , "Contends, debates" , "Quarrels or disagrees" , "Debates or bickers" .)