Aztec emperor (9)
I believe the answer is:
montezuma
'aztec emperor' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for montezuma that I've seen before include "Aztec emperor (who takes his revenge on tourists?)" , "Aztec king, has his Revenge" , "Aztec "revenge" ruler" , "Last Aztec emperor (who now has his revenge!)" , "Last ruler in 16th century of the Aztec empire" .)