Some wheat surplus sent, husk-free (6)
I believe the answer is:
gluten
'some wheat' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Maybe there's an association between them I don't understand?
'surplus sent husk-free' is the wordplay.
'surplus' becomes 'glut' (glut can mean a surplus or surfeit).
'sent husk free' becomes 'en' (I can't justify this - if you can you should give a lot more credence to this answer).
'glut'+'en'='GLUTEN'
Can you help me to learn more?
(Other definitions for gluten that I've seen before include "Substance in cereals" , "Sticky substance" , "Part of wheat" , "Protein found in cereals" , "Protein source" .)