Leave to oneself: not to mention (3,5)

I believe the answer is:

let alone

(Other definitions for let alone that I've seen before include "Not to mention (thing)" , "Don't touch" , "Don't bother someone - allow to be solitary" , "Not to mention - much less - avoid" , "Not to mention, never mind" .)

I've seen this clue in the Sydney Morning Herald.

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