Playing Castle (card game) (4-6)

I believe the answer is:

cat's cradle

'game' is the definition.
(child's game)

'playing castle card' is the wordplay.
'playing' indicates an anagram.
'castle'+'card'='castlecard'
'castlecard' anagrammed gives 'CATS-CRADLE'.

I've seen this clue in The Everyman puzzle in The Observer.

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