Complete circuit is more obese! (7)
I believe the answer is:
rounder
This might be a double definition.
'complete circuit' is the first definition.
(complete circuit of the field in the game rounders)
'more obese' is the second definition.
Both the definition and answer are comparative adjectives. Perhaps there's an association between them I don't understand?
'is' acts as a link.
Can you help me to learn more?
(Other definitions for rounder that I've seen before include "Score at baseball-type game" , "More rotund" , "Or under (anag.)" , "complete circuit in a game" , "Score in bat and ball game" .)