Quartet used in climbs (5)

I believe the answer is:

limbs

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'quartet used' is the definition.
I can't tell whether this definition defines the answer.

'climbs' is the wordplay.
'LIMBS' is hidden within the letters.
But, I am unsure how the hidden word is indicated.

'in' acts as a link.

Can you help me to learn more?

(Other definitions for limbs that I've seen before include "Arms and legs" , "legs, perhaps" .)

I've seen this clue in the Evening Standard.

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