Related Clues:

• Morphine, for one
• Manuscript encl.
• Mailing courtesy: abbr.
• Enc. with a manuscript
• Ready-to-mail item, briefly
• MS accompaniment
• Narcotic drug
• RSVP enclosure
• Enclosure with a MS
• Letter enc.
• Endorphin, basically
• MS. accompanier
• Return mailer (Abbr.)
• Enclosure inside an enclosure, for short
• Encl. to facilitate a response