The most common and most likely answer to this crossword clue is the 9 letter word ALLOWABLE
I've seen this crossword clue in The Times
A
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More clues leading to the result ALLOWABLE
Buddy explains!

The straight part
We know that "it’s permitted" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s permitted = allowable.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 ALLOWABLE mean?
ALLOWABLE noun- Permitted amount or activity.
- Appropriate; satisfactory; acceptable.
- Intellectually admissible; valid; probable.
- Able to be added or deducted in consideration of something.
- Permissible; tolerable; legitimate.
- Praiseworthy.