Sheila gets converted by a prophet (6)
I believe the answer is:
elisha
'a prophet' is the definition.
(Hebrew prophet)
'sheila gets converted' is the wordplay.
'gets converted' is an anagram indicator.
'sheila' is an anagram of 'ELISHA'.
'by' is the link.
(Other definitions for elisha that I've seen before include "Old Testament prophet" , "Hebrew prophet" , "Elijah's successor" , "Prophet; Thirteen across (anag.)" .)