Rising protest must be admitted by state, sooner or later (7)
I believe the answer is:
someday
'sooner or later' is the definition.
(one of these days)
'rising protest must be admitted by state' is the wordplay.
'rising' says the letters should be written backwards (going up in a down clue).
'protest' becomes 'demo' (demonstration).
'must be admitted by' is an insertion indicator.
'state' becomes 'say' (to state something is to say it).
'demo' reversed gives 'omed'.
'omed' placed inside 'say' is 'SOMEDAY'.
(Other definitions for someday that I've seen before include "song" , "When will my prince come" , "eventually" , "At a future time; samoyed (anag.)" , "An unspecified time in the future" .)