The most common and most likely answer to this crossword clue is the 9 letter word SET-ASIDE
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The straight part
We know that "Reserved" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case reserved = set-aside.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 SET-ASIDE mean?
SET-ASIDE noun- Something that is set aside for a specific purpose
- (Britain and Europe) land that has been taken out of agricultural production to reduce crop surpluses
- That has or have been set aside
- Taken out of agricultural production
- Reserved or booked in advance