Chancellor ___ von Bismarck (4)
I believe the answer is:
otto
'chancellor von bismarck' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for otto that I've seen before include "German king" , "German man's name" , "Four-stroke cycle -- palindromic name" , "Rose produces this" , "he goes" .)