Food component gives excess energy to any number (6)
I believe the answer is:
gluten
'food component' is the definition.
(component in some foods)
'excess energy to any number' is the wordplay.
'excess' becomes 'glut' (glut can mean an excess of something).
'energy' becomes 'e' (physics symbol as in E=mc2).
'to any number' becomes 'n' (mathematical symbol for an unspecified number).
'glut'+'e'+'n'='GLUTEN'
'gives' is the link.
(Other definitions for gluten that I've seen before include "Protein in wheat grains" , "Substance in cereals" , "Substance contained in many grains" , "Gluey protein substance in flour" , "Protein found in cereals" .)