The most common and most likely answer to this crossword clue is the 4 letter word FLOG
I've seen this crossword clue in The Times
F
L
O
G
More clues leading to the result FLOG
Buddy explains!

The straight part
We know that "belt" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case belt = flog.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 FLOG mean?
FLOG noun- A contemptible, often arrogant person.
- To whip or scourge someone or something as punishment.
- To use something to extreme; to abuse.
- To sell.
- To steal something.
- To defeat easily or convincingly.
- To exploit.
- A weblog designed to look authentic, but actually developed as part of a commercial marketing strategy to promote some product or service.