Activist theatrical in rage, going wild (10)
I believe the answer is:
campaigner
'activist' is the definition.
(I've seen this before)
'theatrical in rage going wild' is the wordplay.
'theatrical' becomes 'camp' (I've seen this before).
'going wild' is an anagram indicator.
'in'+'rage'='inrage'
'inrage' with letters rearranged gives 'aigner'.
'camp'+'aigner'='CAMPAIGNER'
(Other definitions for campaigner that I've seen before include "Active supporter of a movement" , "Person fighting" , "Militant" , "Advocate" , "Activist" .)