Prophet and ambassador returned to have jail rebuilt (6)
I believe the answer is:
elijah
'prophet' is the definition.
(I know that Elijah is a prophet)
'ambassador returned to have jail rebuilt' is the wordplay.
'ambassador' becomes 'he' (His or Her Excellency).
'returned' says the letters should be written backwards.
'to have' indicates putting letters inside.
'rebuilt' indicates anagramming the letters.
'he' backwards is 'eh'.
'jail' with letters rearranged gives 'lija'.
'eh' going around 'lija' is 'ELIJAH'.
'and' acts as a link.
(Other definitions for elijah that I've seen before include "OT, Islamic prophet" , "Mendelssohn oratorio" , "O.T. prophet who disappeared in fiery chariot" , "Biblical prophet" , "Old Testament prophet" .)