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 within the letters.
However, I'm uncertain 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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