Possible Clues:

• Most hush-hush Potter novel involves short time
• Hush-hush, and a hint to the starred answers' starts
• Doctor protects drug, making injection for certain people only
• Hush-hush operations in Crete upset head of tourism
• Classified source of energy found in new crop test
• Not to be shared
• Dossier stamp
• Note penned by leading faction for minimal circulation
• Sensitive tot creeps about
• Originally suppressed reports etc reclassified as "highly confidential"