What in tarnation is odd for school? (5)
I believe the answer is:
train
'for school?' is the definition.
(school can mean to train or coach)
'what in tarnation is odd' is the wordplay.
I cannot quite understand how this works, but
'in' is within the answer.
The remaining letters 'tra' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for train that I've seen before include "Do exercises" , "Teach (someone) a skill" , "one thing after another" , "guide" , "Retinue; sequence" .)