Reverse across bend (8)
I believe the answer is:
overturn
'reverse' is the definition.
('overturn' can be a synonym of 'reverse')
'across bend' is the wordplay.
'across' becomes 'over' ('over' can be a synonym of 'across').
'bend' becomes 'turn' ('turn' can be a synonym of 'bend'**).
'over'+'turn'='OVERTURN'
(Other definitions for overturn that I've seen before include "Capsize - invalidate" , "Reverses, a decision say" , "Reverse (legal ruling)" , "tip" , "Reverse (decision)" .)