Character periodically going through in last quarter (6)

I believe the answer is:

nature

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

I don't understand the rest of the clue.

(Other definitions for nature that I've seen before include "Essence; kind" , "The physical world" , "mother, so-called" , "Fundamental character" , "Tea urn (anag)" .)

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