The most common and most likely answer to this crossword clue is the 7 letter word DAYBOOK
I've seen this crossword clue in Financial Times
D
A
Y
B
O
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K
Buddy explains!
The straight part
We know that "Where transactions might appear" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case where transactions might appear = daybook.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 DAYBOOK mean?
DAYBOOK noun- A daily chronicle; a diary.
- (bookkeeping) A ledger; an accounting journal.
- A logbook.