Fatally uninteresting (6)
I believe the answer is:
deadly
This clue might be a double definition.
'fatally' is the first definition.
Both the answer and definition are adverbs. Perhaps there's an association between them I don't understand?
'uninteresting' is the second definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I can't see?
Can you help me to learn more?
(Other definitions for deadly that I've seen before include "No small bore" , "Lethal, could be fatal" , "Lethal or mortal" , "sniper aspires to be" , "There are seven such sins" .)