Over-weight beer? (5)
I believe the answer is:
stout
'beer?' is the definition.
(type of beer)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for stout that I've seen before include "Resolute" , "Portly - type of dark beer" , "Dark beer for the rather fat" , "Fat; dependable" , "tipple" .)