Such a hole as to make you stare? (6)

I believe the answer is:

gaping

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'such' is the definition.
Both the answer and definition are adjectives. Maybe they are linked in a way I don't understand?

I cannot understand how the remainder of the clue works.

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(Other definitions for gaping that I've seen before include "With the mouth wide open, in wonder perhaps" , "Yawning" , "Opening mouth wide or staring in wonder" , "Staring open-mouthed" .)

I've seen this clue in the Evening Standard.

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