Related Clues:

• Insert of a sort: Abbr
• Short return always comes back to you
• Britannica, for one: Abbr
• Freelancer's encl
• "5W-30" preceder
• Env. stuffing
• S.A.S.E., e.g.: Abbr
• Pkg. insert
• Fan mail encl
• Letter abbr
• Cause of an env. bulge
• Ltr.-bottom letters
• RSVP encl
• Ref. wk
• Enclosure to an ed