Doddering, I left, possibly being seen out (6)

I believe the answer is:

senile

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'doddering' is the definition.
(I know that doddering can be written as senile)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for senile that I've seen before include "In one's dotage" , "Mentally infirm with age" , "Mentally weak due to old age" , "Suffering from mental weakness due to old age" , "Old and doddery" .)

I've seen this clue in the Evening Standard.

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