Go up an octave (5)

I believe the answer is:

scale

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'go up' is the definition.
(scaling is a kind of going up)

I don't understand the rest of the clue.

(Other definitions for scale that I've seen before include "Go up" , "Doh, ray, me" , "Ratio between size and representation, on map say" , "Graduated table" , "An ordered series of units for measurement purposes" .)

I've seen this clue in The Irish Independent.

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