Crew's perfection hard to ignore (5)

I believe the answer is:

eight

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'crew's' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for eight that I've seen before include "Four twos" , "Half a quarter" , "4 x 2" , "Number that figures in ice-skating?" , "Cube of two" .)

I've seen this clue in The Telegraph.

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