Surplus weight produced by one who eats too much (7)
I believe the answer is:
glutton
'one who eats too much' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'surplus weight produced by' is the wordplay.
'surplus' becomes 'glut' (glut can mean a surplus or surfeit).
'weight' becomes 'ton' (unit of weight).
'produced by' says to put letters next to each other.
'glut'+'ton'='GLUTTON'
Can you help me to learn more?
(Other definitions for glutton that I've seen before include "Excessive eater; wolverine" , "Big eater" , "Greedy type" , "One who eats to excess" , "One could visit several restaurants!" .)