Possible Clues:

• 'To be hooked, put a further one to the hundred on it, as they say in advertising (9)'
• Cocaine involved in increasing dependency
• Reckoning in a way without Conservative's bad habit
• Extra is divided by 100 � it's hard to take away
• 100 in calculation that's difficult to eliminate
• Out of habit, did badly in battle
• H and a bit more that one's had to get rid of
• Did badly in fighting drug dependency
• How the jargon of advertising may become a habit