Possible Clues:

• Old boy tucked into cold-filled tortilla for a quid perhaps
• American explorer brought back to company ... this!
• Important Colonial cash crop
• Weedy type deemed to be unhealthy
• To reversing taxi, starts to call out: 'Put that in your pipe and smoke it!'
• Turns up, officer has a reputation for taking money off criminals with good books in nicotine plant
• Commander and navigator retired for shag?
• Heartless abbot rejects carbon copy from order and leaves for a smoke
• Plant with narcotic leaves
• Addictive leaf