Possible Clues:

• Friend we would back may, at a stretch, be 16 at the front?
• Loose skin below the throat
• Hanging fold of skin on a person's neck
• In a flap we had knocked back drink
• Mate got married, keeled over creating a bit of a flap
• Skin hanging from neck
• Fold of skin initially described expertly with love and patience
• Fold of skin on the throat
• Friend married on the rebound, causing a flap
• Feature of an iguana's neck