Venetian ruler (4)
I believe the answer is:
doge
'venetian ruler' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for doge that I've seen before include "Old chief magistrate in Venice and Genoa" , "Title of former ruler of Venice" , "Historically, the chief magistrate of Venice or Genoa" , "Chief of ancient Venice" , "Ancient lord of Venice" .)