Clue: Physicist using volume to wedge faulty Aga door (8)
Answer: AVOGADRO
Explanation: Definition: Physicist
**V**(olume) *used to wedge* ***(aga door)** 
*Refers to Count Amadeo (1776–1856), Italian physicist and chemist, famous for his work on gases. Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules".