Copier, first character in school to cheat and first in exam (6)
I believe the answer is:
scribe
'copier' is the definition.
(I've seen this in another clue)
'first character in school to cheat and first in exam' is the wordplay.
'first character in school' becomes 's' (1st letter of 'school').
'to cheat' becomes 'crib' (cribbing is a kind of cheating).
'and' means one lot of letters go next to another.
'first in exam' becomes 'e' (1st letter of 'exam').
's'+'crib'+'e'='SCRIBE'
(Other definitions for scribe that I've seen before include "Letter-writer of old" , "Copier of (handwritten) documents" , "A writer of old" , "Clerk, a public copyist" , "Official writer" .)