Patron saint has doctor brought in again (6)
I believe the answer is:
andrew
'patron saint' is the definition.
(patron saint of Scotland)
'doctor brought in again' is the wordplay.
'doctor' becomes 'dr' (abbreviation).
'brought in' means one lot of letters goes inside another.
'again' becomes 'anew' (synonyms).
'dr' put inside 'anew' is 'ANDREW'.
'has' is the link.
(Other definitions for andrew that I've seen before include "Wander (anag)" , "Boy's name" , "November thirtieth is this saint's day" , "Warden (anag.)" , "Ex-Poet Laureate" .)