"Das Kapital" author (4)
I believe the answer is:
marx
'das kapital author' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for marx that I've seen before include "Groucho's surname" , "Karl, top communist" , "Das Kapital author" , "Communist founder" , "Founder of communism" .)