Cuban leader since 1959 (6)
I believe the answer is:
castro
'cuban leader since 1959' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for castro that I've seen before include "Fidel or Ral" , "Cuban dictator" , "Cuban leader, d. 2016" , "Fidel -, former Cuban leader" , "He's late" .)