Time for a revolution? (4)
I believe the answer is:
year
'time for a revolution?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for year that I've seen before include "Complete cycle of seasons" , "Group of students" , "One intake of undergrads" , "See 33 Across" , "Period of just over 52 weeks" .)