Teacher or giver (5)
I believe the answer is:
donor
'giver' is the definition.
(I know that giver can be written as donor)
'teacher or' is the wordplay.
'teacher' becomes 'don' (don can mean an academic - especially at Oxbridge).
'don'+'or'='DONOR'
(Other definitions for donor that I've seen before include "One giving to a cause" , "Someone providing" , "One who gives something" , "Maker of gift" , "One who gives blood, for instance" .)