The most common and most likely answer to this crossword clue is the 9 letter word FACTORING
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The straight part
We know that "business involving debts" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case business involving debts = factoring.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 FACTORING mean?
FACTORING verb- To find all the factors of (a number or other mathematical object) (the objects that divide it evenly).
- (of a number or other mathematical object) To be a product of other objects.
- (commercial) To sell a debt or debts to an agent (the factor) to collect.
- A financial transaction whereby a business sells its accounts receivable to a third party (called a factor) at a discount.
- The process of factorization.