Possible Clues:

• To understand nearly all of Italy is a drug
• Prepare to get on computer endlessly — it's a kind of drug
• It might blooming well fox them to have this on hand and take a spade to it with a sail (9)
• Heart drug prepared from foxglove leaves
• It'd do your heart good to put your finger on a broken sail
• Figure it is about a quid for the drug
• Might one finger sail with this from 4 across
• Drug, you have to understand, is taken round country after being cut
• Under your finger, the foxglove gets the sail twisted
• Its leaves are used as a heart stimulant