Denied access in revolutionary study (7)
I believe the answer is:
negated
'denied' is the definition.
(I've seen this in another clue)
'access in revolutionary study' is the wordplay.
'access' becomes 'gate' (I've seen this in other clues).
'in' is an insertion indicator.
'revolutionary' says the letters should be written in reverse.
'study' becomes 'den' (term for a study or office).
'den' reversed gives 'ned'.
'gate' going within 'ned' is 'NEGATED'.
(Other definitions for negated that I've seen before include "Denied" , "Made ineffective" , "Discredited" , "Abrogated" , "Nullified" .)