As a rule, the creep ordered a pint (7)
I believe the answer is:
precept
'as a rule the' is the definition.
I can't judge whether this definition defines the answer.
'creep ordered a pint' is the wordplay.
'ordered' is an anagram indicator.
'a pint' becomes 'pt' (abbreviation).
'creep' with letters rearranged gives 'prece'.
'prece'+'pt'='PRECEPT'
Can you help me to learn more?
(Other definitions for precept that I've seen before include "General rule for behaviour" , "Rule of conduct or doctrine" , "Rule or principle" , "Rule of conduct - maxim" , "Rule of conduct or command" .)