The most common and most likely answer to this crossword clue is the 4 letter word PAID
I've seen this crossword clue in Financial Times
P
A
I
D
More clues leading to the result PAID
- Settled with priest’s help
- Settled up quietly with help
- Parking subsidy is spent
- Assistant under pressure brought in
- Settled one into residence
- Settled softly with relief
- Apartment in which one’s settled
- Parking fine daughter settled
- Minimal money help is given as wages
- Put money in machine, maybe, parking? Help!
Buddy explains!

The straight part
We know that "Settled up" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case settled up = paid.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 PAID mean?
PAID verb- To give money or other compensation to in exchange for goods or services.
- To discharge, as a debt or other obligation, by giving or doing what is due or required.
- To be profitable for.
- To give (something else than money).
- To be profitable or worth the effort.
- To discharge an obligation or debt.
- To suffer consequences.
- To admit that a joke, punchline, etc., was funny.
- That is not free of charge; that costs money.
- Rich, wealthy