A monastic superior with a single reasoning from deduction (1,6)
I believe the answer is:
a priori
'reasoning from deduction' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'a monastic superior with a single' is the wordplay.
I cannot really understand how this works, but
'a' is within the answer.
'superior' could be 'prior' (prior is a kind of superior) and 'prior' is present in the answer.
'single' could be 'i' (one) and 'i' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for a priori that I've seen before include "Way of reasoning" , "Based on theory (Latin)" , "Like reasoning from cause to effect" , "'Derived by logic, without observed facts (1,6)'" , "How Romans spoke as far as one knows" .)