Prophet in jail: he cracked (6)
I believe the answer is:
elijah
'prophet' is the definition.
(I know that Elijah is a prophet)
'jail he cracked' is the wordplay.
'cracked' is an anagram indicator.
'jail'+'he'='jailhe'
'jailhe' with letters rearranged gives 'ELIJAH'.
'in' acts as a link.
(Other definitions for elijah that I've seen before include "O.T. prophet who disappeared in fiery chariot" , "Mendelssohn oratorio" , "OT, Islamic prophet" , "Biblical prophet" , "Hebrew prophet who rebuked Ahab and Jezebel" .)