Posting without first or last bit (6)

I believe the answer is:

ending

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'last bit' is the definition.
'ending' can be an answer for 'last' (I've seen this before). I'm not sure about the 'bit' bit.

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for ending that I've seen before include "Coda" , "Putting a stop to" , "ultimately" , "Bringing to a close" , "Closing down" .)

I've seen this clue in The Mirror.

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