### Clue: A pelmet husband installed; too much and too sudden (9)
### Answer: AVALANCHE 
 ### Explanation: Definition: too much and too sudden
 A + VALANCE(a pelmet, which is used to hide curtain fittings above a window) **containing**(… installed) H(abbrev. for "husband").
Defn: One has to presume "Something that is …" is implicitly in front of the definition to make it a noun, as the answer is.