Feudal slave (4)
'feudal slave' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for serf that I've seen before include "Feudal labourer" , "Feudal estate worker" , "'In the Middle Ages, a person owned by a feudal lord (4)'" , "Person required to work for a lord" , "One bound to work" .)
'feudal slave' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for esne that I've seen before include "Domestic slave in Anglo-Saxon times" , "Drudge" .)