Art movement to stop up surrounding platform (7)
I believe the answer is:
'art movement' is the definition.
(Dadaism is an example)
'stop up surrounding platform' is the wordplay.
'stop up' becomes 'dam' (I've seen this in another clue).
'surrounding' is an insertion indicator.
'platform' becomes 'dais' (dais is a kind of platform).
'dam' enclosing 'dais' is 'DADAISM'.
'to' acts as a link.
(Other definitions for dadaism that I've seen before include "artistic movement" , "Early twentieth century art movement" , "Absurd movement" , "Anti-art movement" .)