City in Belgium; capital of Hainaut province (4)
I believe the answer is:
mons
I believe this clue is a double definition.
'city in belgium' is the first definition.
(I've seen this in another clue)
'capital of hainaut province' is the second definition.
(I know that Mons capital of Hainaut)
(Other definitions for mons that I've seen before include "Battlefield" , "Belgian town" , "place of conflict?" , "Belgian World War One battle site" , "First major battle of World War I" .)