Possible Clues:

• Method of encryption or set of rules
• Cryptographic system
• It takes brains to crack it
• Word with fire or area
• Symbolically, in E this will keep Pa in control
• Moral guidelines broken at GCHQ?
• Regulatory system on fish numbers
• Computer programmer's work
• After a century the poet writes it in a secret way
• Cryptogram or set of standards