Possible Clues:

• The weed
• Put that in your pipe and smoke it!
• Snuff, for example
• Plant associated with serious health risks
• Eg, shag or snuff
• Weed
• For a change, Cabot & Co goes up in smoke
• Boot out airman caught entering Virginia, say
• Explorer set up company for product discovered in America
• Weed Italian explorer brought back, returning round cape