Scornful (8)
'scornful' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for derisive that I've seen before include "'Scornful, mocking (8)'" , "Expressing contempt" , "Taunting" , "Contemptuous" .)
(Other definitions for sardonic that I've seen before include "Cynical -- so rancid (anag)" , "Disdainfully or ironically humorous" , "sneering" , "Scornfully mocking" , "Dry, cynically mocking" .)
(Other definitions for scathing that I've seen before include "Harshly critical" , "Severely critical" , "Sarcastic" , "Scornfully critical" , "Caustic" .)
'scornful' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sniffy that I've seen before include "Scornful, contemptuous" , "Disdainful" , "Supercilious; snobby" .)