Fat man I married needs new top (5)
I believe the answer is:
tubby
'fat' is the definition.
('tubby' can be similar in meaning to 'fat')
I cannot understand how the remainder of the clue works.
(Other definitions for tubby that I've seen before include "Rather overweight" , "Plump" , "Looking round" , "Short and rather fat" , "Roly-poly" .)