Said to change platform (4)
I believe the answer is:
dais
'platform' is the definition.
(I know that dais is a type of platform)
'said to change' is the wordplay.
'to change' indicates an anagram.
'said' anagrammed gives 'DAIS'.
(Other definitions for dais that I've seen before include "Platform, rostrum" , "Said (anag.)" , "stands on this?" , "stepping up here?" , "stage" .)