The ceremony right within the CIA guiding principles (8)
I believe the answer is:
criteria
'guiding principles' is the definition.
The answer and definition can be both related to thinking as well as being plural nouns.
Perhaps they are linked in a way I don't understand?
'the ceremony right within the cia' is the wordplay.
'the ceremony' becomes 'rite' (rite is a kind of ceremony).
'right' becomes 'r' (common abbreviation).
'within' means one lot of letters goes inside another.
'rite'+'r'='riter'
'riter' placed inside 'cia' is 'CRITERIA'.
Can you help me to learn more?
(Other definitions for criteria that I've seen before include "Benchmarks" , "Standards, yardsticks" , "Principles on which to base a judgement" , "Standards on which to base judgements" , "Ideals" .)