### Clue: Any wrinkling in lettuce is a result of oxygen deficiency (8)
### Answer: CYANOSIS 
 ### Explanation: Definition: a result of oxygen deficiency
An envelope ('in') of YAN, an anagram ('wrinkling') of 'any' in COS ('lettuce') plus 'is'. A bluish discoluration of the skin as a result of lack of oxygen in the blood.