The most common and most likely answer to this crossword clue is the 7 letter word SWIVELS
I've seen this crossword clue in Financial Times
S
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Buddy explains!
The straight part
We know that "couplings" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case couplings = swivels.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 SWIVELS mean?
SWIVELS noun- A piece, as a ring or hook, attached to another piece by a pin, in such a manner as to permit rotation about the pin as an axis.
- A small piece of ordnance, turning on a point or swivel; called also swivel gun.
- Strength of mind or character that enables one to overcome adversity; confidence; force of will.
- A rotating of the hips.
- To swing or turn, as on a pin or pivot.