Short, even to a grasshopper? (4-4)

I believe the answer is:

knee-high

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'short' is the definition.
(thesaurus)

I don't understand the remainder of the clue.

(Other definitions for knee-high that I've seen before include "Not reaching the thigh" , "Covering the lower leg" , "Up to half a leg in depth" , "Only up to one's patella" , "Reaching halfway up one's legs" .)

I've seen this clue in the Sydney Morning Herald.

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