Maker of some new theatrical headgear? (6)

I believe the answer is:

hatter

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'maker' is the definition.
(hatter is a kind of maker)

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

(Other definitions for hatter that I've seen before include "There's a mad one in 'Alice's Adventures in Wonderland'" , "Tea-party attender" , "Milliner" , "Tea-party holder" , "There's a Mad one in 'Alice in Wonderland'" .)

I've seen this clue in the Evening Standard.

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