Retro work by youngster is a type of picture book (5)

I believe the answer is:

popup

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'a type of picture book' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'retro work by youngster' is the wordplay.
'retro' says the letters should be written in reverse (retro is Latin for 'backwards').
'work' becomes 'op' (short for opus).
'by' is a charade indicator (letters next to each other).
'youngster' becomes 'pup' (a pup is a young dog).
'op' written backwards gives 'po'.
'po'+'pup'='POPUP'

'is' acts as a link.

Can you help me to learn more?

(Another definition for popup that I've seen is " What 11 [TOAST] might do".)

I've seen this clue in The Irish Times.

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