Crossword Genius

They’re beyond belief at hold-ups (8)

Ross

I believe the answer is:

atheists

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'they're beyond belief' is the definition.
The definition suggests an adverb but the answer is not.

'at hold-ups' is the wordplay.
'hold-ups' becomes 'heists' (I've seen this in another clue).
'at'+'heists'='ATHEISTS'

Can you help me to learn more?

(Other definitions for atheists that I've seen before include "They believe there are no gods" , "ungodly crew" , "Heathens" , "They don't believe in a deity" , "People who believe there is no god" .)

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