Idea of negative charged particle (6)
I believe the answer is:
notion
'idea' is the definition.
(I know that notion is a type of idea)
'negative charged particle' is the wordplay.
'negative' becomes 'not' (I've seen this in another clue).
'charged particle' becomes 'ion' (I've seen this in another clue).
'not'+'ion'='NOTION'
'of' acts as a link.
(Other definitions for notion that I've seen before include "Idea or whim" , "Vague impression" , "desire" , "Whimsical idea or small sewing article" , "Idea, concept" .)