Possible Clues:

• 'I ___ with my little eye . . .'
• Unwelcome plant?
• Secret Squirrel, e.g
• Use a hidden camera, say
• One who may bug you
• Austin Powers, e.g
• Stealth song off "Morrison Hotel" (with "The")?
• Espionage expert
• Invasive plant?
• He came in from the cold