Argues (6)
'argues' is the definition.
('debate' can be a synonym of 'argue')
This is all the clue.
(Other definitions for debates that I've seen before include "Formal discussions" , "Discusses" .)
(Other definitions for pleads that I've seen before include "Implores" , "Appeals or requests earnestly" , "Begs" , "Makes appeal or entreaty" .)