Christian missionary and saint in a bar (7)
I believe the answer is:
apostle
'christian missionary' is the definition.
(I've seen this before)
'saint in a bar' is the wordplay.
'saint' becomes 'st' (abbreviation).
'in' indicates putting letters inside.
'bar' becomes 'pole' ().
'a'+'pole'='apole'
'st' placed within 'apole' is 'APOSTLE'.
'and' acts as a link.
(Other definitions for apostle that I've seen before include "Divine messenger" , "Leaps to find religious follower" , "St James, for example" , "Peter, perhaps" , "Maybe Peter" .)