50s Oscar-winner beginning to rattle someone victimised (6)
I believe the answer is:
martyr
If this is the answer I cannot explain how the clue works.
Can you help me to learn more?
(Other definitions for martyr that I've seen before include "One dying for belief" , "Person dying for a cause" , "One killed for faith" , "may be one hounded to death" , "put at stake?" .)