Uncharged particle (7)
I believe the answer is:
neutron
'uncharged particle' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for neutron that I've seen before include "Elementary particle with zero charge" , "one isn't charged" , "Uncharged subatomic particle" , "On tuner (anag.)" , "Charged particle" .)