The most common and most likely answer to this crossword clue is the 4 letter word LARD
I've seen this crossword clue in The Times
L
A
R
D
More clues leading to the result LARD
- Fat boy cramming in last of burger
- Fat vicar's bottom pinched by groom
- Fat fellow about right
- Fat landlord must lose a bit in the middle
- Fat boy eating another, ultimately
- Primarily, lipoid adiposity rendered digestible?
- Fat young man having right to tuck in
- Animal product causing some vascular disease
- Note by doctor about fat
- Fat boy runs inside
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 = lard.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 LARD mean?
LARD noun- Fat from the abdomen of a pig, especially as prepared for use in cooking or pharmacy.
- Fatty meat from a pig; bacon, pork.
- To stuff (meat) with bacon or pork before cooking.
- To smear with fat or lard.
- To garnish or strew, especially with reference to words or phrases in speech and writing.
- To fatten; to enrich.
- To grow fat.
- To mix or garnish with something, as by way of improvement; to interlard.