Belgian city lord (5)
I believe the answer is:
liege
I believe this is a double definition.
'belgian city' is the first definition.
(I've seen this before)
'lord' is the second definition.
(I have seen 'Feudal lord' mean 'liege' so perhaps 'lord' could also mean 'liege')
(Other definitions for liege that I've seen before include "Owing feudal allegiance" , "Belgian city on Meuse" , "Loyal vassal" , "Chieftain" , "Belgian city or feudal superior" .)