Old peacekeepers when safe go it alone: UN formed (6,2,7)

I believe the answer is:

league of nations

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'old peacekeepers when' is the definition.
I can't tell whether this defines the answer.

'safe go it alone un formed' is the wordplay.
'formed' indicates anagramming the letters.
'safe'+'go'+'it'+'alone'+'un'='safegoitaloneun'
'safegoitaloneun' is an anagram of 'LEAGUE OF NATIONS'.

Can you help me to learn more?

(Other definitions for league of nations that I've seen before include "Pacific group" , "international organisation" , "Old pacifists" .)

I've seen this clue in The Times.

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