Class bright guy I snubbed (5)
I believe the answer is:
genus
'class' is the definition.
(I've seen this before)
'bright guy i snubbed' is the wordplay.
'bright guy' becomes 'genius' (bright or clever person).
'snubbed' indicates named letters should be taken away.
'genius' with 'i' taken out is 'GENUS'.
(Other definitions for genus that I've seen before include "Class of animal" , "Taxonomic grouping" , "The Homo of Homo sapiens?" , "species grouped together" , "Category between family and species" .)