Theologian got high with a doctor (7)
I believe the answer is:
ambrose
'theologian' is the definition.
(I know that Ambrose is a theologian)
'got high with a doctor' is the wordplay.
'got high' becomes 'arose' (I've seen this in another clue).
'with' is an insertion indicator.
'a doctor' becomes 'MB' (Bachelor of Medicine).
'arose' placed around 'mb' is 'AMBROSE'.
(Other definitions for ambrose that I've seen before include "Early saint; - Bierce, author" , "Bishop of Milan once" , "Curtly perhaps" , "saint, maybe" , "Church Father" .)