Human possibility of being a prophet (5)
I believe the answer is:
nahum
'a prophet' is the definition.
(I know that Nahum is a prophet)
'human possibility' is the wordplay.
'possibility' indicates anagramming the letters (another possible arrangement of the letters).
'human' with letters rearranged gives 'NAHUM'.
'of being' acts as a link.
(Other definitions for nahum that I've seen before include "Destruction-of-Nineveh prophet" , "Old Hebrew prophet" , "Minor prophet" , "Prophet's book" , "Hebrew prophet - Biblical book" .)