Conclusion delayed in mixed set of rules (4)
I believe the answer is:
code
'set of rules' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for code that I've seen before include "Ethical standards" , "what's character-changing?" , "See 12" , "Secret system of letters. words etc" , "System of ethics - cipher" .)