Student upset choral society’s leader (7)
I believe the answer is:
scholar
'student' is the definition.
(I know that student can be written as scholar)
'upset choral society's leader' is the wordplay.
'upset' indicates anagramming the letters.
'leader' says to take the initial letters.
The initial letter of 'societys' is 's'.
'choral'+'s'='chorals'
'chorals' anagrammed gives 'SCHOLAR'.
(Other definitions for scholar that I've seen before include "Academic; pupil" , "university type?" , "Distinguished academic" , "Person of learning" , "Learned type" .)