Pleas to become a disciple (7)
I believe the answer is:
apostle
'a disciple' is the definition.
(the apostles were disciples of Jesus)
'pleas to become' is the wordplay.
'become' indicates an anagram.
'pleas'+'to'='pleasto'
'pleasto' is an anagram of 'APOSTLE'.
(Other definitions for apostle that I've seen before include "Originally, one sent to preach the gospel" , "Good man" , "Peter, perhaps" , "To lapse (anag) - ardent supporter of a cause" , "Ardent espouser of new system" .)