Writer's offspring a rich family member (10)

I believe the answer is:

rothschild

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'a rich family member' is the definition.
The definition suggests a singular noun which matches the answer.

'writer's offspring' is the wordplay.
'writer's' becomes 'Roth's' (novelist Philip Roth).
'offspring' becomes 'child' (child is a kind of offspring).
'roths'+'child'='ROTHSCHILD'

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I've seen this clue in The Guardian.

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