Student's small choral composition (7)
I believe the answer is:
scholar
'student's' is the definition.
(scholar is a kind of student)
'small choral composition' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'composition' indicates anagramming the letters.
'choral' is an anagram of 'cholar'.
's'+'cholar'='SCHOLAR'
(Other definitions for scholar that I've seen before include "Learned (or learning) one" , "Academic; pupil" , "Academic, schoolboy" , "Learned type" , "Person of learning" .)