The most common and most likely answer to this crossword clue is the 11 letter word TIMESHARING
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Buddy explains!

The straight part
We know that "Vacationers’ arrangement" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case vacationers’ arrangement = timesharing.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 TIMESHARING mean?
TIMESHARING noun- The joint ownership or lease of a property by multiple people who can only use it for specified periods every year, or every other year.
- A technique that allows many users to use a central computer simultaneously through remote terminals.