Shopkeeper is said to have got fatter (7)
I believe the answer is:
grosser
'fatter' is the definition.
('gross' can be similar in meaning to 'fat')
'shopkeeper is said' is the wordplay.
'shopkeeper' becomes 'grocer' (I've seen this before).
'is said' shows a homophone (sound like).
'grocer' is a homophone of 'GROSSER'.
'to have got' is the link.
(Other definitions for grosser that I've seen before include "More corpulent" , "more vulgar" .)