One bell resembling another? (6)

I believe the answer is:

ringer

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

I don't understand the rest of the clue.

(Other definitions for ringer that I've seen before include "One is almost identical to another in the belfry" , "Campanologist's" , "pulling Tom?" , "One calling" , "One making the toll" .)

I've seen this clue in the Evening Standard.

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