The most common and most likely answer to this crossword clue is the 8 plus 5 letter word SPENDING MONEY
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Buddy explains!
The straight part
We know that "necessary for expenses" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case necessary for expenses = spending money.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 SPENDING MONEY mean?
SPENDING MONEY noun- A sum of cash kept in one's personal possession, for routine expenses or incidental purchases.