Cardinal put factor 50 over area (9)
I believe the answer is:
elemental
'cardinal' is the definition.
Both the answer and definition are adjectives. Perhaps there's an association between them I don't understand?
'factor 50 over area' is the wordplay.
'factor' becomes 'element' (synonyms).
'e0' becomes 'l' (Roman numeral).
'over' is an insertion indicator.
'area' becomes 'a' (maths abbreviation).
'element'+'l'='elementl'
'elementl' enclosing 'a' is 'ELEMENTAL'.
'put' acts as a link.
Can you help me to learn more?
(Other definitions for elemental that I've seen before include "Basic, primitive" , "Of basic importance" , "Let me lean like forces of nature" , "Fundamental; supernatural entity" , "Of nature's powers" .)