Possible Clues:

• Overhear organ piece that goes to the head
• What you might do with a bug or a creepy-crawly
• Be nosy, say, when eating a brownie, oddly
• Listen in
• Scuttling insect
• An insect — I wager (anag)
• Insect shell-like on rug
• Bug?
• For one hiding war criminal, I listen in
• Insect, caught by eg Darwin, without wings