Emperor fled leaving Otranto (4)
I believe the answer is:
otto
'emperor' is the definition.
(I've seen this before)
'fled leaving otranto' is the wordplay.
'fled' becomes 'ran' (ran away).
'leaving' suggests deleting specific letters.
'otranto' with 'ran' removed is 'OTTO'.
(Other definitions for otto that I've seen before include "Something oily" , "German man's name" , "German king" , "Reversible German" , "Male German name - a palindrome" .)