Diagrammatic form of catechism (9)
I believe the answer is:
schematic
'diagrammatic' is the definition.
Both the answer and definition are adjectives. Perhaps there's a link between them I don't understand?
'form of catechism' is the wordplay.
'form of' indicates an anagram (the letters need to be in another 'form').
'catechism' is an anagram of 'SCHEMATIC'.
Can you help me to learn more?
(Other definitions for schematic that I've seen before include "Represented by a diagram" , "In the form of a diagram or chart" , "Symbolic diagram" , "Catechism (anag) - of a diagram" , "Represented in simplified form" .)