Film about British revolutionary (5)
I believe the answer is:
rebel
'revolutionary' is the definition.
(I know that rebel is a type of revolutionary)
'film about british' is the wordplay.
'film' becomes 'reel' (reel is a kind of film).
'about' means one lot of letters goes inside another.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'reel' placed around '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" .)