One addressing envelopes in other apparent order (6)

I believe the answer is:

orator

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

I don't understand how the remainder of the clue works.

(Other definitions for orator that I've seen before include "A Rhetorical talker or speech-maker" , "An impressive public speaker" , "One who holds forth" , "Rhetorician" , "A fluent public speaker" .)

I've seen this clue in The Independent.

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