The opposition's contention? (7)
I believe the answer is:
rivalry
This could be a double definition.
'the opposition's' is the first definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'contention?' is the second definition.
('rivalry' can be a synonym of 'contention')
Can you help me to learn more?
(Other definitions for rivalry that I've seen before include "Vendetta" , "Competition" .)