Fat porter, perhaps? (5)
I believe the answer is:
stout
'fat' is the definition.
(similar in meaning)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for stout that I've seen before include "Thick; beer" , "tipple" , "Heavily built; beer" , "Portly - porter" , "Round" .)