How to delay an attack by robbers (4,2)

I believe the answer is:

hold up

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'delay an attack by robbers' is the definition.
'hold up' can be an answer for 'delay' (synonyms). I am not certain of the 'an attack by robbers' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for hold up that I've seen before include "Survive" , "jam" , "Exhibit" , "Delay" , "robbery" .)

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

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