Clue: Heartless upstart right to cut gas for which there's no charge (7)
Answer: NEUTRON
Explanation: Definition: for which there's no charge
 [ **All inner letters deleted from**(Heartless) "upstart" + R(abbrev. for "right") ] **contained in**(to cut) NEON(an inert gas).
Defn: A subatomic particle without an electric charge.