Is the pressure applied with them measurable in bars? (6)

I believe the answer is:

levers

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'bars?' is the definition.
(lever is a kind of bar)

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

(Other definitions for levers that I've seen before include "They are used to prise things open" , "Prises, jimmies" , "They are pivoted on fulcrums" , "Rigid bars pivoted about a fulcrum" , "Prising bars" .)

I've seen this clue in the Evening Standard.

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