Winter Palace occupant (4)
I believe the answer is:
tsar
'winter palace occupant' 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 "Once-powerful Russian" , "Russian ruler (S, not Z)" , "Eg, Ivan the Terrible" , "Star for a Russian emperor" , "Male monarch" .)