One student, generous but narrow-minded (9)
I believe the answer is:
illiberal
'narrow-minded' is the definition.
(similar in meaning)
'one student generous' is the wordplay.
'one' becomes 'i' (Roman numeral).
'student' becomes 'l' (as in L-plates for learner drivers).
'generous' becomes 'liberal' (similar in meaning).
'i'+'l'+'liberal'='ILLIBERAL'
'but' is the link.
(Other definitions for illiberal that I've seen before include "Restrictive" , "Narrow-minded" , "Intolerant; reactionary" , "Intolerant; ungenerous" , "unenlightened?" .)