The most common and most likely answer to this crossword clue is the 7 letter word SOLARIA
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More clues leading to the result SOLARIA
Buddy explains!

The straight part
We know that "spa rooms" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case spa rooms = solaria.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 SOLARIA mean?
SOLARIA noun- An establishment with sunbeds in it or where one can rent sunbeds.
- A room, with many windows, exposed to the sun.
- A sundial.