Newly arrived it is put back inside and reserved (8)

I believe the answer is:

reticent

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'reserved' is the definition.
(synonyms)

I can't explain the rest of the clue.

(Other definitions for reticent that I've seen before include "Quiet" , "Not revealing one's thoughts readily" , "Reserved, not revealing thoughts readily" , "Reserved, shy" , "Close-lipped" .)

I've seen this clue in The Globe and Mail.

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