Explosive charge shown by Australian swimmer after leaving hotel party (7)

I believe the answer is:

torpedo

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

I don't understand the remainder of the clue.

(Other definitions for torpedo that I've seen before include "Sub's missile" , "Explosive missile from submarine" , "American sandwich made with a long split roll" , "Such as could sink" , "Self-propelled submarine weapon" .)

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