Revolutionaries got tiaras wrong (9)
I believe the answer is:
agitators
'revolutionaries' is the definition.
(I've seen this before)
'got tiaras wrong' is the wordplay.
'wrong' is an anagram indicator.
'got'+'tiaras'='gottiaras'
'gottiaras' with letters rearranged gives 'AGITATORS'.
(Other definitions for agitators that I've seen before include "We wind up" , "revolutionaries" , "A gait rots the stirrers" , "Rabble-rousers" .)