Pearl’s beautiful mother (5)

I believe the answer is:

nacre

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'mother' is the definition.
(I have seen 'Mother of pearl ' mean 'nacre' so perhaps 'mother' could also mean 'nacre')

I can't explain the remainder of the clue.

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(Other definitions for nacre that I've seen before include "Mother-of-pearl - crane (anag)" , "valuable material" , "inside of shell" , "Constituent of inlay furniture" , "Pearl's mum" .)

I've seen this clue in the Evening Standard.

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