Hardback! (5)

I believe the answer is:

stern

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'hardback' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?

This is the entire clue.

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(Other definitions for stern that I've seen before include "Grimly serious; back" , "Severe, forbidding" , "Unsmiling" , "Looking severe" , "Harsh at the back of the ship" .)

I've seen this clue in the Sydney Morning Herald and The Globe and Mail.

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