Setter: artless fop, I suspect about average (7,2,5)
I believe the answer is:
plaster of paris
'setter' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'artless fop i suspect about average' is the wordplay.
'suspect' indicates anagramming the letters.
'about' indicates putting letters inside.
'average' becomes 'par' (I've seen this before).
'artless'+'fop'+'i'='artlessfopi'
'artlessfopi' anagrammed gives 'plasterofis'.
'plasterofis' enclosing 'par' is 'PLASTER OF PARIS'.
Can you help me to learn more?
(Other definitions for plaster of paris that I've seen before include "What might make cast" , "material for cast" , "is needed for the cast?" .)