Finish off fast with extremely huge pastry (6)

I believe the answer is:

quiche

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'pastry' is the definition.
(I know that quiche is a type of tart)

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

(Other definitions for quiche that I've seen before include "Cheese and bacon pastry dish" , "Open tart with savoury egg filing" , "food" , "Type of savoury tart" , "French dish?" .)

I've seen this clue in the Sydney Morning Herald.

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