Crossword Genius

A rule which is flexible (4,7)

Ross

I believe the answer is:

tape measure

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'a rule' is the definition.
(I know that tape measure is a type of rule)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for tape measure that I've seen before include "one might have a few feet on it" , "Flexible strip showing lengths" , "Device for finding length of cloth etc" , "band covering the distance?" , "Tailors may use one" .)

I've seen this clue in The Globe and Mail.
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