Capital point - everything forms an old barrier (6,4)

I believe the answer is:

berlin wall

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'an old barrier' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.

'capital point everything' is the wordplay.
'capital' becomes 'berlin' (capital of Germany).
'point' becomes 'w' (W is an example).
'everything' becomes 'all' (all things).
'berlin'+'w'+'all'='BERLIN WALL'

'forms' acts as a link.

Can you help me to learn more?

I've seen this clue in The Daily Express.

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