Intellectual one in class (6)
I believe the answer is:
genius
'intellectual one in class' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'intellectual one in class' is the wordplay.
'intellectual one' becomes 'i' (Roman numeral. I am not sure about the 'intellectual' bit.).
'in' indicates putting letters inside.
'class' becomes 'genus' (I've seen this before).
'i' going inside 'genus' is 'GENIUS'.
Can you help me to learn more?
(Other definitions for genius that I've seen before include "One has exceptional ability" , "Person with exceptional creative ability" , "no dope" , "Person with unusual mental ability" , "egghead" .)