Humorously sarcastic (6)
I believe the answer is:
ironic
'humorously sarcastic' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ironic that I've seen before include "likely to provoke a wry smile" , "Sarcastically humorous" , "Sneering" , "Mockingly humorous" , "These words express the opposite of the literal meaning" .)