Recall the German revolutionary (3)
I believe the answer is:
red
'revolutionary' is the definition.
(red can informally mean communist)
'recall the german' is the wordplay.
'recall' says the letters should be written backwards.
'the german' becomes 'der' ('the' in German).
'der' backwards is 'RED'.
(Other definitions for red that I've seen before include "14 -- breed of 4" , "Colour of blood" , "Colour for a blusher" , "Looking embarrassed" , "socialist?" .)