Vague idea (6)

I think it could be either:

notion

motion

'vague idea' is the definition.
(I've seen this before)

This is the entire clue.

(Other definitions for notion that I've seen before include "Vague understanding" , "Vague or fanciful idea" , "Idea, concept" , "Whimsical idea or small sewing article" , "Idea or fancy" .)

I've seen this clue in The Sunday Times, The Times, The Guardian and the Penny Press.

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