Topping things to wear (4)

I believe the answer is:

hats

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But I can't explain it at all! Could you help me understand?

(Other definitions for hats that I've seen before include ""Porkpie" and "pillbox" attire" , "Headwear" , "Headdresses" , "Headgear" , "Milliner's stock" .)

I've seen this clue in the Evening Standard.

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