One who doesn’t believe cashiers at bank robbery (5)

I believe the answer is:

heist

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'bank robbery' is the definition.
(I've seen this in another clue)

I don't understand the rest of the clue.

(Other definitions for heist that I've seen before include "Armed hold-up (sl.)" , "Armed robbery" , "Mugging" , "crime?" , "Audacious robbery" .)

I've seen this clue in The Hindu.

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