Son not showing up in brief class (3)

I believe the answer is:
ilk
'class' is the definition.
(both can mean a type or variety)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ilk that I've seen before include "Type of milksop" , "Disposition" , "Type - kind" , "Sort or type of silks" , "Of that kind or sort" .)
