Tell tales of Serpent swallowing own tail (5)

I believe the answer is:

sneak

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'tell tales' is the definition.
(to sneak on someone is to tell tales about them)

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for sneak that I've seen before include "Underhanded tell-tale" , "In school, tell tales" , "thief" , "Prowl" , "Go furtively and tell tales" .)

I've seen this clue in The Independent.

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