An instrument of Eve's downfall (7)

I believe the answer is:

serpent

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'an instrument' is the definition.
(serpent is a kind of instrument)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for serpent that I've seen before include "Large snake; sly person" , "Large snake, dragon" , "Early wind instrument" , "Scaly reptile" , "Limbless reptile" .)

I've seen this clue in The Globe and Mail.

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