Titan
'titan' is the definition.
(I know that titan can be written as giant)
This is the entire clue.
(Other definitions for giant that I've seen before include "Superhuman being" , "Creature of exceptional size" , "A mighty man like Goliath or Carnera" , "James Dean film (big one!)" , "Large black and white mammal" .)
(Other definitions for czar that I've seen before include "Despot" , "Russian ruler (alt. but not rare spelling)" , "person of great power" , "Russian emperor" , "Pre-1917 Russian ruler" .)