Related Clues:

• Cavern sound
• Olfactory stimulator
• Sound heard in a cave
• Delta follower
• Bounceback
• One may be disagreeable
• Off-the-wall response?
• It may be picked up in a locker
• Comeback of a sort
• Must, e.g.
• Olfactory stimulus
• Chamber phenomenon
• Yodeler's feedback
• ''What died?'' provocation
• Gasoline additive