Platform adopted by crazy revolutionary movement (7)
I believe the answer is:
dadaism
'movement' is the definition.
(Dadaism is an example)
'platform adopted by crazy revolutionary' is the wordplay.
'platform' becomes 'dais' (dais is a kind of platform).
'adopted by' indicates putting letters inside (I've seen this in other clues).
'crazy' becomes 'mad' ('mad' can be a synonym of 'crazy').
'revolutionary' says the letters should be written backwards.
'mad' backwards is 'dam'.
'dais' put within 'dam' is 'DADAISM'.
(Other definitions for dadaism that I've seen before include "Anti-art movement" , "artistic movement" , "Absurd movement" , "Early twentieth century art movement" .)