Security system initially captured criminals targeting vault (4)

I believe the answer is:

cctv

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'security system' is the definition.
I know nothing about this answer so I can't judge whether this works.

'initially captured criminals targeting vault' is the wordplay.
'initially' says to take the initial letters.
The first letters of 'captured criminals targeting vault' is 'CCTV'.

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I've seen this clue in The Irish Times.

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