Act nine or younger, daughter! (7)

I believe the answer is:

pretend

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'act' is the definition.
(I know that pretend is a more specific form of act)

I cannot understand how the rest of the clue works.

(Other definitions for pretend that I've seen before include "Simulate, feign" , "Simulated" , "Suppose" , "Dissemble" , "Simulate - make up" .)

I've seen this clue in The Times.

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