Tubular kind of hat? (5)

I believe the answer is:

straw

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'hat?' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

(Other definitions for straw that I've seen before include "Dried stalks; yellow" , "Stalk of dry grass" , "Dried stalks for fodder" , "The last one broke the camel's back" , "Animal bedding" .)

I've seen this clue in the Evening Standard.

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