### Clue: Killer in wood, wife smiled devilishly in repose (5,3,7)
### Answer: DUTCH ELM DISEASE 
 ### Explanation: Definition: Killer in wood
 DUTCH(one's wife, especially among Cockneys, from "duchess") + [ **anagram of**(… devilishly) SMILED **contained in**(in) EASE(repose/in a state of comfort) ].
Defn: …, specifically elm trees.