The most common and most likely answer to this crossword clue is the 5 plus 4 letter word ORDER FORM
I've seen this crossword clue in Financial Times
O
R
D
E
R
F
O
R
M
More clues leading to the result ORDER FORM
Buddy explains!
The straight part
We know that "Requisition" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case requisition = order form.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.