Related Clues:

• Program
• Computer language
• Secret language
• Spy's writing
• See 15-Across
• It may be cracked
• Spy's secret
• Principles
• Pig Latin, e.g.
• Spy's writing, perhaps
• Secret message
• One if by land, two if by sea, etc.
• Kind of word
• Value system
• Genetic or dress follower