Pack up for post, possibly (4)

I believe the answer is:

stop

I'm a little stuck... Click here to teach me more about this clue!

'pack up' is the definition.
'stop' can be an answer for 'pack' (thesaurus). I am unsure of the 'up' bit.

'post possibly' is the wordplay.
'possibly' indicates anagramming the letters.
'post' with letters rearranged gives 'STOP'.

'for' is the link.

Can you help me to learn more?

(Other definitions for stop that I've seen before include "Hold on" , "Come to a halt" , "Blockage" , "Knock out" , "period in US" .)

I've seen this clue in the Evening Standard.

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