The most common and most likely answer to this crossword clue is the 9 letter word PENDULUMS
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Buddy explains!

The straight part
We know that "Swingers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case swingers = pendulums.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 PENDULUMS mean?
PENDULUMS noun- A body suspended from a fixed support so that it swings freely back and forth under the influence of gravity, commonly used to regulate various devices such as clocks.
- A lamp, etc. suspended from a ceiling.
- A watch's guard-ring by which it is attached to a chain.