Initially lord is entitled governing enslaved subject (5)
I believe the answer is:
liege
'subject' is the definition.
(thesaurus)
'initially lord is entitled governing enslaved' is the wordplay.
'initially' indicates taking the first letters.
The first letters of 'lord is entitled governing enslaved' is 'LIEGE'.
(Other definitions for liege that I've seen before include "Province of Belgium" , "Belgian city or feudal superior" , "Feudal lord or Belgian city" , "Owing feudal allegiance" , "European city" .)