Lord of a Belgian province (5)
I believe the answer is:
liege
This clue is a double definition.
'lord' is the first definition.
(feudal term for a superior)
'a belgian province' is the second definition.
(Liege is a province of Belgium)
'of' acts as a link.
(Other definitions for liege that I've seen before include "World War one battle site" , "Old sovereign" , "Chieftain" , "Belgian city or ancient lord" , "Feudal (lord); vassal" .)