The most common and most likely answer to this crossword clue is the 9 letter word CORPULENT
I've seen this crossword clue in The Daily Telegraph
C
O
R
P
U
L
E
N
T
More clues leading to the result CORPULENT
- Fat, but puds halved in my dieting period!
- Port uncle drunk getting fat
- Couple wantonly gobbling ultimate burger won’t half get fat
- About to get rich without initially running to fat
- Let cop run amok showing signs of greed?
- Large clubs put loner off
- Fat copper holds reason for coming up with time for fasting
- Stout heart receives tug, almost not heartless
- Fat Charlie gets rich importing rubies originally
- Money collected fast — not small but huge
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 = corpulent.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 CORPULENT mean?
CORPULENT adjective- Large in body; fat; overweight.
- Physical, material, corporeal.