Attorney with information to act badly somewhere in Greater London (8)
I believe the answer is:
dagenham
'somewhere in greater london' is the definition.
'attorney with information to act badly' is the wordplay.
'attorney' becomes 'da' (District Attorney).
'with' means one lot of letters go next to another.
'information' becomes 'gen' (gen is a kind of information).
'to act badly' becomes 'ham'.
'da'+'gen'+'ham'='DAGENHAM'
(Other definitions for dagenham that I've seen before include "Eastern area in Greater London" , "In car manufacturing centre" , "Essex town" , "Barking and -, London borough" , "Area of east London" .)