Clue: Affect with drug, producing odd reaction laced with sulphur (9)
Answer: NARCOTISE
Explanation: Definition: Affect with drug
An envelope ('laced with') of S (chemical symbol, 'sulphur' aka sulfur) in NARCOTIE, an anagram ('odd') of 'reaction'. Yes, it is a straight anagram, but this parsing makes sense of 'laced with'.