Alphabetic characters (7)
I believe the answer is:
letters
'alphabetic characters' is the definition.
('letter' can be a synonym of 'alphabetic character')
This is the entire clue.
(Other definitions for letters that I've seen before include "Epistles" , "They may indicate a degree" , "Items of mail" , "providing digs?" , "A, B, C, D etc" .)