Posh car turns over (5)
I believe the answer is:
rolls
I believe this is a double definition.
'posh car' is the first definition.
(I've seen this before)
'turns over' is the second definition.
('roll' can be a synonym of 'turn over')
(Other definitions for rolls that I've seen before include "Lists of names of members" , "flash car" , "breakfast food" , "Overturns -- luxury car" , "Official lists" .)