The most common and most likely answer to this crossword clue is the 4 plus 9 letter word BANK STATEMENT
I've seen this crossword clue in The Times
B
A
N
K
S
T
A
T
E
M
E
N
T
More clues leading to the result BANK STATEMENT
- Rely on New Testament as money-related document
- Rely on say number in police showing an indication of interest?
- ‘I’m by the river’ possibly interpreted as current account?
- Bet on politicians to siphon off a dollar, tweak source of financial document
- Comings and goings in brief?
- Listing for balance — something pronounced on slope?
Buddy explains!

The straight part
We know that "money-related document" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case money-related document = bank statement.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.