Belgian legislation overturned by twit (7)
I believe the answer is:
walloon
'belgian' is the definition.
(Walloons are an ethnic group of Wallonia, Belgium)
'legislation overturned by twit' is the wordplay.
'legislation' becomes 'law' (I've seen this before).
'overturned' is a reversal indicator.
'by twit' becomes 'loon' (I can't explain this - if you can you should give a lot more credence to this answer).
'law' backwards is 'wal'.
'wal'+'loon'='WALLOON'
Can you help me to learn more?
(Other definitions for walloon that I've seen before include "Southern Belgian" , "Francophone" , "European" , "Belgian dialect" , "Native of S Belgium or N France area" .)