When arresting marines, peacekeeping organisation first removes weapons (6)

I believe the answer is:

unarms

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'when arresting marines peacekeeping organisation first removes weapons' is the definition.
I can't judge whether this definition defines the answer.

'when arresting marines peacekeeping organisation first' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'arresting' indicates putting letters inside.
'marines' becomes 'RM' (abbreviation for 'Royal Marines').
'peacekeeping organisation' becomes 'UN' (United Nations).
'first' means one lot of letters go next to another.
'as' placed around 'rm' is 'arms'.
'arms' after 'un' is 'UNARMS'.

Can you help me to learn more?

(Another definition for unarms that I've seen is " Takes away the weapons from".)

I've seen this clue in The Independent.

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