Hamster and duck chewed old bread (11)

I believe the answer is:

deutschmark

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'old bread' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.

'hamster and duck chewed' is the wordplay.
'and' is a charade indicator (letters next to each other).
'chewed' indicates an anagram.
'hamster' after 'duck' is 'duckhamster'.
'duckhamster' anagrammed gives 'DEUTSCHMARK'.

Can you help me to learn more?

(Another definition for deutschmark that I've seen is " Former German currency".)

I've seen this clue in the Sydney Morning Herald.

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