Magazine a failure, it’s ticking along (4,4)

I believe the answer is:

time bomb

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But I can't explain it at all! Could you help me understand?

(Other definitions for time bomb that I've seen before include "Its detonation is delayed" , "Detonating mechanism with clock" , "one could go off after a while" , "Exploding ticker?" , "Device set to explode later" .)

I've seen this clue in The Hindu.

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