Excess weight? It's his danger (7)
I believe the answer is:
glutton
'his danger' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'excess weight?' is the wordplay.
'excess' becomes 'glut' (glut can mean an excess of something).
'weight?' becomes 'ton' (unit of weight).
'glut'+'ton'='GLUTTON'
'it's' is the link.
Can you help me to learn more?
(Other definitions for glutton that I've seen before include "Excessive eater; wolverine" , "One eats too much" , "Gourmand" , "Gormandizer" , "Big eater" .)