Teacher of Old Testament, stuck in rut, heading north (5)
I believe the answer is:
tutor
'teacher' is the definition.
(tutor is a kind of teacher)
'old testament stuck in rut heading north' is the wordplay.
'old testament' becomes 'ot'.
'stuck in' means one lot of letters goes inside another.
'heading north' shows that the letters should be reversed in order.
'ot' inserted into 'rut' is 'rotut'.
'rotut' in reverse letter order is 'TUTOR'.
'of' acts as a link.
(Other definitions for tutor that I've seen before include "college teacher" , "Personal teacher" , "Edify" , "Teach" , "Give individual instruction" .)