Crossword Genius

Basic requirement of an office machine (6)

Ross

I believe the answer is:

staple

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'basic' is the definition.
(synonyms)

I cannot understand how the rest of the clue works.

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(Other definitions for staple that I've seen before include "essential" , "Fastening device" , "key" , "Main, important" , "Main - way to fasten paper" .)

I've seen this clue in the Evening Standard.
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