Warned about disciple (6)
I believe the answer is:
andrew
'disciple' is the definition.
(I know that Andrew is a Apostle)
'warned about' is the wordplay.
'about' indicates an anagram.
'warned' anagrammed gives 'ANDREW'.
(Other definitions for andrew that I've seen before include "- - Marr (TV)" , "Boy's name" , "Patron saint of Scotland, Russia" , "Composer of many musicals ..." , "apostle" .)