Communist: the German revolutionary (3)
I believe the answer is:
red
'communist' is the definition.
(red is a kind of communist)
'the german revolutionary' is the wordplay.
'the german' becomes 'der' ('the' in German).
'revolutionary' says the letters should be written in reverse.
'der' reversed gives 'RED'.
(Other definitions for red that I've seen before include "Type of wine" , "socialist?" , "Scarlet or vermilion" , "Crimson" , "Carmine" .)