The most common and most likely answer to this crossword clue is the 9 letter word BLACKMAIL
I've seen this crossword clue in The Daily Telegraph
B
L
A
C
K
M
A
I
L
Buddy explains!
The straight part
We know that "It’s a crime" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it’s a crime = blackmail.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 BLACKMAIL mean?
BLACKMAIL noun- The extortion of money by threats of public accusation, exposure, or censure.
- A form of protection money (or corn, cattle, etc.) anciently paid, in the north of England and south of Scotland, to the allies of robbers in order to be spared from pillage.
- Black rent, or rent paid in corn, meat, or the lowest coin, as opposed to white rent, which was paid in silver.
- Compromising material that can be used to extort someone, dirt.
- To extort money or favors from (a person) by exciting fears of injury other than bodily harm, such as injury to reputation, distress of mind, false accusation, etc.
- (Kenya) To speak ill of someone; to defame someone.