Unpopped corn (6)
I believe the answer is:
kernel
'unpopped corn' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for kernel that I've seen before include "Inner part of nut" , "Seed in hard shell" , "Core of a nut" , "Stone" , "Edible or central part of nut" .)