Possible Clues:

• Amp attachment
• Label on a cassette recorder jack
• It may be open at a comedy club
• What a DJ speaks into
• Lapel attachment for an interview
• ___ drop (triumphant gesture after a winning performance)
• One may be open at the bar
• Karaoke machine part
• Source of unwelcome feedback, informally?
• Hot ___ (speaker's worry)