Make mistake promoting academic (3)
I believe the answer is:
don
'academic' is the definition.
(type of academic - especially at Oxbridge)
'make mistake promoting' is the wordplay.
I cannot quite see how this works, but
'make' could be 'do' (do can mean to make or prepare) and 'do' is located in the answer.
A single letter 'n' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for don that I've seen before include "University lecturer" , "River, academic" , "Put on; lecturer" , "A Spanish grandee like Quixote" , "Put on clothes like noss" .)