Hardback! (5)

I believe the answer is:

stern

I'm a little stuck... Click here to teach me more about this clue!

'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.

Can you help me to learn more?

(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 Globe and Mail and the Sydney Morning Herald.

Want a hint initially instead of a full solution? Install my app