Tender young model? (4-6)

I believe the answer is:

baby-sitter

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'tender' is the definition.
Both the answer and definition are singular nouns.
Maybe you can see a link between them that I can't see?

'young model?' is the wordplay.
'young' becomes 'baby' (baby is a kind of young).
'model?' becomes 'sitter' (I've seen this before).
'baby'+'sitter'='BABY-SITTER'

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