Crossword Genius

A girl returned holding Latin stamp (5,5)

Ross

I believe the answer is:

penny black

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

'stamp' is the definition.
Both the definition and answer are singular nouns.
Maybe there's an association between them I don't understand?

'a girl returned holding latin' is the wordplay.
'a girl' becomes 'penny' (woman's name).
'returned' becomes 'back' (I've seen this before).
'holding' indicates putting letters inside.
'latin' becomes 'l'.
'back' going around 'l' is 'black'.
'penny'+'black'='PENNY BLACK'

Can you help me to learn more?

(Other definitions for penny black that I've seen before include "World's first adhesive postage stamp, 1840" , "Today one would be unlikely to lick this" , "when without means to send a letter" , "first to get licked" .)

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