Record - one about reasoning (5)
I believe the answer is:
logic
'reasoning' is the definition.
(I've seen this before)
'record one about' is the wordplay.
'record' becomes 'log' (log is a kind of record).
'one' becomes 'I' (Roman numeral).
'about' becomes 'c' (abbreviation for 'circa').
'log'+'i'+'c'='LOGIC'
(Other definitions for logic that I've seen before include "Sound sense" , "Aristotelian theories" , "The science of reasoning correctly" , "Rigorous reasoning" , "Branch of philosophy that analyses inference" .)