The most common and most likely answer to this crossword clue is the 10 letter word PLAYGROUND
I've seen this crossword clue in Financial Times
P
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More clues leading to the result PLAYGROUND
- Drop an ugly misbehaving group of children here
- Nuisance mentioned on every side in holiday region
- Where you may find children with no class?
- Holiday region has infestation mentioned on every side
- In which someone may be out of his or her class?
- Where children might enjoy quiet wager on good game of golf?
- Quiet place, establish asĀ parkĀ
Buddy explains!

The straight part
We know that "holiday region" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case holiday region = playground.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 PLAYGROUND mean?
PLAYGROUND noun- (outdoors) A large open space for children to play on, usually having dedicated play equipment (such as swings and slides).
- Any physical or metaphysical space in which a person or organization has free rein to do as they please.