Crossword Genius

Surprised at bone spurs (nothing cut out) — that's being rude! (10)

Ross

I believe the answer is:

abruptness

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'surprised at bone' is the definition.
The definition and answer can be both human attributes as well as being singular nouns.
Maybe you can see an association between them that I don't see?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for abruptness that I've seen before include "Curtness" , "Curt rudeness" .)

I've seen this clue in The Guardian.
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