Wasting billions, perhaps Trident alarm sounds permanently (3,5)

I believe the answer is:

for keeps

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'permanently' is the definition.
(I've seen this before)

I don't understand the remainder of the clue.

(Other definitions for for keeps that I've seen before include "with serious intent" , "indefinitely" , "in favour of strongholds" , "Permanently (colloq.)" , "Always" .)

I've seen this clue in The Independent.

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