The most common and most likely answer to this crossword clue is the 9 letter word TAMPERING
I've seen this crossword clue in Independent
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More clues leading to the result TAMPERING
Buddy explains!
The straight part
We know that "messing around" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case messing around = tampering.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 TAMPERING mean?
TAMPERING verb- To make unauthorized or improper alterations, sometimes causing deliberate damage; to meddle (with something).
- To try to influence someone, usually in an illegal or devious way; to try to deal (with someone).
- To meddle (with something) in order to corrupt or pervert it.
- To involve oneself (in a plot, scheme, etc.).
- To attempt to practise or administer something (especially medicine) without sufficient knowledge or qualifications.
- (in professional sports) To discuss future contracts with a player, against league rules.
- The act of one who tampers.