The most common and most likely answer to this crossword clue is the 5 letter word OBESE
O
B
E
S
E
More clues leading to the result OBESE
- People honoured trade, finally, with large corporation?
- Old boy and earl eating last bits of mince pies might become thus
- In Tacitus by the way see developing porky
- Before end of parade, medals far too heavy
- Sulphur found in old beer, mostly stout
- Rather large robes employed, but not all
- Robes expanding to disguise fat
- Needing to diet? Number going outside to be seen
- Alumnus feasted regularly, appearing thus?
- One gets this often by eating something enticing initially
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 = obese.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 OBESE mean?
OBESE adjective- Extremely overweight, especially: weighing more than 20% (for men) or 25% (for women) over their ideal weight determined by height and build; or, having a body mass index over 30 kg/m2.