Revolutionary role as local ruler (6)
I believe the answer is:
satrap
'local ruler' is the definition.
(term for a provincial ruler in the Persian Empire)
'revolutionary role as' is the wordplay.
'revolutionary' says the letters should be written in reverse.
'role' becomes 'part' (eg a part or role in a film).
'part'+'as'='partas'
'partas' reversed gives 'SATRAP'.
(Other definitions for satrap that I've seen before include "Old Persian governor took a seat to start" , "A sprat for the old governor of Persia" , "despotic ruler" , "Persian provincial governor" , "Old head" .)