The fairest of the fair (3,6)

I believe the answer is:

ash blonde

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

I cannot understand how the remainder of the clue works.

(Other definitions for ash blonde that I've seen before include "Hair colouring" , "Description of shock" , "fair hair" , "lady with light hair" , "silver-haired type" .)

I've seen this clue in the Evening Standard.

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