Creature with eight legs - and the rest! (6)

I believe the answer is:

spider

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

I cannot understand how the remainder of the clue works.

(Other definitions for spider that I've seen before include "One has eight legs" , "Black widow or redback?" , "potter's accessory?" , "Web developer" , "Webster" .)

I've seen this clue in The Telegraph.

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