Conservative up to date spoiled takeover (4,5)
I believe the answer is:
coup detat
'takeover' is the definition.
(I have seen 'Hostile takeover' mean 'coup detat' so perhaps 'takeover' could also mean 'coup detat')
'conservative up to date spoiled' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'spoiled' indicates an anagram.
'up'+'to'+'date'='uptodate'
'uptodate' with letters rearranged gives 'oupdetat'.
'c'+'oupdetat'='COUP DETAT'
(Other definitions for coup detat that I've seen before include "Sudden change of government by force" , "revolutionary action" , "Unconstitutional overthrow of a government" , "Hostile takeover" , "Sudden, perhaps violent, overthrow of a government" .)