Nagasaki terror weapon? (3)

I believe the answer is:

gas

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'nagasaki terror weapon?' is the definition.
I can't judge whether this defines the answer.

'nagasaki terror weapon?' is the wordplay.
'GAS' is hidden in amongst the letters.
But, I am unsure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for gas that I've seen before include "rabbit" , "THIRD PART OF 23" , "Petrol (US)" , "Eg, nitrogen" , "It may be natural" .)

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