Robust defending principle of judge and one revolutionary prophet (6)

I believe the answer is:

elijah

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'prophet' is the definition.
(I know that Elijah is a prophet)

I can't explain the remainder of the clue.

(Other definitions for elijah that I've seen before include "OT, Islamic prophet" , "Hebrew prophet who disappeared in fiery chariot" , "Old Testament prophet" , "Biblical prophet" , "Mendelssohn oratorio" .)

I've seen this clue in The Telegraph.

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