Follow eastern ruler (4)
I believe the answer is:
doge
'ruler' is the definition.
(I have seen 'Venetian ruler ' mean 'doge' so perhaps 'ruler' could also mean 'doge')
'follow eastern' is the wordplay.
'follow' becomes 'dog' (dog can mean to follow or torment).
'eastern' becomes 'e'.
'dog'+'e'='DOGE'
(Other definitions for doge that I've seen before include "Old lord of Venice" , "foreign magistrate" , "Venetian ruler" , "Chief of ancient Venice" , "Historically, the chief magistrate of Venice or Genoa" .)