Possible Clues:

• In a clandestine and unobtrusive way
• Secretly repair to Net headquarters
• Secretly not daft, comprehending the question
• Privately
• Secretly hearing about the attractive girl
• Ninja-like, and this puzzle's theme
• Secretly goes a little quiet on the end
• A guest of David Dimbleby keeping your secret?
• May perhaps, first off, question opening film, secretly
• Surreptitiously ... and a hint to 20-, 28-, 46- and 52-Across