The most common and most likely answer to this crossword clue is the 7 letter word PAUNCHY
P
A
U
N
C
H
Y
More clues leading to the result PAUNCHY
Buddy explains!

The straight part
We know that "Fat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fat = paunchy.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PAUNCHY mean?
PAUNCHY adjective- Having a paunch; having a prominent stomach; potbellied.