Clue: Funny stuff derived from coffee (substitute an 'e' for 'o') (9)
Answer: CHICANERY
Explanation: Definition: Funny stuff
CHICORY with O replaced by AN E. Chicory is used as a coffee substitute or flavouring, but it seems a bit of a stretch to *define* it as "coffee" (and adding "derived from" doesn't help)
 *As explained by Eileen and Hillbilly below: it's "coffee substitute [with] AN E for O (ignoring the cheeky brackets). I even wrote "substitute" in my explanation and didn't notice it was also in the clue – d'oh!)