A bit of a nerve, pinching Juliet's rear? One's not charged (7)
I believe the answer is:
neutron
'one's not charged' is the definition.
(I've seen this before)
'a bit of a nerve pinching juliet's rear?' is the wordplay.
'a bit of a nerve' becomes 'neuron'.
'pinching' means one lot of letters goes inside another (taking inside).
'rear?' indicates one should take the final letters (the back of the word).
The final letter of 'juliet' is 't'.
'neuron' going around 't' is 'NEUTRON'.
(Other definitions for neutron that I've seen before include "Elementary particle with zero charge" , "Particle that decays when released" , "Subatomic particle with no electric charge" , "Uncharged particle in a nucleus" , "Chargeless particle" .)