Movement in barrier surrounding platform (7)
I believe the answer is:
dadaism
'movement' is the definition.
(Dadaism is an example)
'barrier surrounding platform' is the wordplay.
'barrier' becomes 'dam' (dam is a kind of barrier).
'surrounding' means one lot of letters goes inside another.
'platform' becomes 'dais' (dais is a kind of platform).
'dam' placed around 'dais' is 'DADAISM'.
'in' is the link.
(Other definitions for dadaism that I've seen before include "Absurd movement" , "Early twentieth century art movement" , "artistic movement" , "Anti-art movement" .)