Bygone ruler (4)
'bygone ruler' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for tsar that I've seen before include "Rats (anag)" , "Once-powerful Russian" , "Russian ruler (S, not Z)" , "Word derived from Caesar, used by European rulers since 1547" , "Russian leader" .)
'bygone ruler' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for czar that I've seen before include "person of great power" , "Pre-1917 Russian ruler" , "Despot" , "Russian emperor" , "policy coordinator" .)