Crossword Genius

Army member is firing all guns together (5)

Ross

I believe the answer is:

salvo

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'army' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for salvo that I've seen before include "Unusual excuse" , "Burst of firing" , "Burst of artillery shots" , "reservation" , "Aussie evangelist" .)

I've seen this clue in the Sydney Morning Herald.
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