Curious how system creates stem (4)

I believe the answer is:

nosy

'curious' is the definition.
(similar in meaning)

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

(Other definitions for nosy that I've seen before include "Prying, snoopy" , "Offensively curious or inquisitive" , "Meddlesome" , "Inquisitive in nasal manner" , "Fragrant" .)

I've seen this clue in The Guardian.

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