Antagonist displays an absence of activity (10)
I believe the answer is:
stagnation
'activity' is the definition.
The definition and answer can be both states of affairs as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'antagonist displays an absence' is the wordplay.
'antagonist' anagrams to 'STAGNATION'.
But, I am not sure how this is indicated.
'of' is the link.
Can you help me to learn more?
(Other definitions for stagnation that I've seen before include "Nothing much happens" , "Cessation of movement" , "It's still" , "movement's antithesis?" , "making no progress" .)