Judge to be a female fathead? (6)

I believe the answer is:

assess

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'judge' is the definition.
(to assess is to judge or rate)

I don't understand the remainder of the clue.

(Other definitions for assess that I've seen before include "Rate, evaluate" , "Estimate, decide the value of" , "Judge the quality of" , "Place a value on" , "Estimate, gauge" .)

I've seen this clue in the Evening Standard.

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