Tiny part in slogan Reaganites used? (8)

I believe the answer is:

electron

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'tiny part' is the definition.
'electron' can be an answer for 'part' (I have seen 'Part of atom ' mean 'electron' so perhaps 'part' could also mean 'electron'). I am not certain of the 'tiny' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for electron that I've seen before include "There's not much to it" , "One's charged" , "Negatively charged particle" , "Particle found in all atoms" , "Part of atom" .)

I've seen this clue in The Sun.

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