One climbs on them to be weighed, presumably! (6)

I believe the answer is:

scales

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'one climbs' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for scales that I've seen before include "Fish flake or weighing device" , "Measuring instrument for weighing" , "7 [SIGN OF THE ZODIAC] representative" , "Fish flakes or measuring devices" , "Climbs - balances" .)

I've seen this clue in the Evening Standard.

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