Pre-1917 Russian ruler (4)
I believe the answer is:
tsar
'pre-1917 russian ruler' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tsar that I've seen before include "One associated with 26 [KREMLIN]" , "Old Russian ruler" , "A former Russian ruler - rats to him" , "Male monarch" , "Person in charge" .)