Peter perhaps bitter about job (7)
I believe the answer is:
apostle
'peter perhaps' is the definition.
(peter is a kind of Apostle)
'bitter about job' is the wordplay.
'bitter' becomes 'ale' ('ale' can be a synonym of 'bitter').
'about' indicates putting letters inside.
'job' becomes 'post' (post is a kind of job).
'ale' placed around 'post' is 'APOSTLE'.
(Other definitions for apostle that I've seen before include "Peter, perhaps" , "Good man" , "Champion - one of twelve" , "Teacher of new faith or movement" , "James, perhaps" .)