Not bothered when one went off on one’s own (4,5)

I believe the answer is:

left alone

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'not bothered when one' is the definition.
I can't judge whether this defines the answer.

'went off on one's own' is the wordplay.
'went off' becomes 'left' (as in leaving. I am not sure about the 'off' bit.).
'on one's own' becomes 'alone' (I've seen this before).
'left'+'alone'='LEFT ALONE'

Can you help me to learn more?

(Another definition for left alone that I've seen is " Allowed to remain undisturbed".)

I've seen this clue in the Evening Standard.

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