Teacher’s tedious course interrupted by books being returned (5)
I believe the answer is:
tutor
'teacher's' is the definition.
(tutor is a kind of teacher)
'tedious course interrupted by books being returned' is the wordplay.
'tedious course' becomes 'rut' (I have seen 'predictable course' mean 'rut' so perhaps 'course' could also mean 'rut'. I am not sure about the 'tedious' bit.).
'interrupted by' means one lot of letters goes inside another.
'books' becomes 'OT' (abbreviation for Old Testament).
'being returned' says the letters should be written in reverse.
'rut' enclosing 'ot' is 'rotut'.
'rotut' backwards is 'TUTOR'.
Can you help me to learn more?
(Other definitions for tutor that I've seen before include "class leader" , "Teach" , "Coach, teacher" , "trainer" , "Private or university teacher" .)