Rock adder? (6)

I believe the answer is:

totter

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'rock' is the definition.
(I know this)

I can't explain the rest of the clue.

(Other definitions for totter that I've seen before include "adder?" , "Sway, as if about to fall" , "Scrap dealer" , "Walk shakily as if about to fall" , "Be unsteady on one's feet" .)

I've seen this clue in The Globe and Mail, The Telegraph and the Sydney Morning Herald.

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