Film about British revolutionary (5)
I believe the answer is:
rebel
'revolutionary' is the definition.
(rebel is a kind of revolutionary)
'film about british' is the wordplay.
'film' becomes 'reel' (reel is a kind of film).
'about' indicates putting letters inside.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'reel' enclosing 'b' is 'REBEL'.
(Other definitions for rebel that I've seen before include "Kick over the traces" , "One who's risen in opposition" , "One who rises up" , "Dissident" , "Flouter of authority" .)