Notion middleman takes every so often (4)

I believe the answer is:

idea

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'notion' is the definition.
(both can mean a thought)

I can't explain the remainder of the clue.

(Other definitions for idea that I've seen before include "Creative spark" , "Mental impression" , "Brainwave" , "Product of the mind" , "Inkling" .)

I've seen this clue in The Irish Times.

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