Possible Clues:

• Opposite of pref
• Add-on to the end of a word: Abbr.
• Add-on to the end of a wd
• End-of-word add-on Abbr.:
• End-of-word addn.
• -ed, e.g.: Abbr.
• Wd. ending
• '-er' or '-ing,' e.g.: Abbr.