Wheels around Zulu leader (4)
I believe the answer is:
'leader' is the definition.
(I know that czar is a type of monarch)
'wheels around zulu' is the wordplay.
'wheels' becomes 'car' (car wheel is a kind of wheel).
'around' indicates putting letters inside.
'zulu' becomes 'Z' (phonetic alphabet: alpha, bravo, charlie etc.).
'car' going around 'z' is 'CZAR'.
(Other definitions for czar that I've seen before include "Pre-1917 Russian ruler" , "Russian ruler (alt. but not rare spelling)" , "person of great power" , "Russian emperor" , "policy coordinator" .)