Fat — stout (5)
I believe the answer is:
obese
I believe this clue is a double definition.
'fat' is the first definition.
(similar in meaning)
'stout' is the second definition.
(I've seen this in another clue)
(Other definitions for obese that I've seen before include "Huge" , "Needing to lose weight" , "carrying remarkable weight" , "round" , "Unhealthily large" .)