Charging account supported by United States in heart of Belgium (8)
I believe the answer is:
accusing
'charging' is the definition.
('accuse' can be a synonym of 'charge')
'account supported by united states in heart of belgium' is the wordplay.
'account' becomes 'acc'.
'supported by' means one lot of letters go next to another (in a down clue, some letters hold up others).
'united states' becomes 'US' (abbreviation for the United States).
'heart of' says to take the centre.
The centre of 'belgium' is 'g'.
'acc'+'us'+'in'+'g'='ACCUSING'
(Other definitions for accusing that I've seen before include "Charging (someone with crime)" , "Charging with an offence" , "Indicting" , "Levelling a charge against" .)