Debated, contended (6)
I believe the answer is:
argued
I believe this clue is a double definition.
'debated' is the first definition.
('argue' can be a synonym of 'debate')
'contended' is the second definition.
('argue' can be a synonym of 'contend')
(Other definitions for argued that I've seen before include "Sought to show by reasoning" , "Rag due (anag.)" , "Bickered" , "Disputed, opposed verbally" , "Wrangled" .)