Clue: Cell deaths topped small number Puck's got cross about (8)
Answer: NECROSIS
Explanation: Definition: Cell deaths
[*topped*] (o)**NE** ("small number") +** I **("Puck") *got* **CROSS** *about* 
*Shame that Puck didn't use a synonym of CROSS as 5/8ths of the answer is in the clue.