Critically, disastrously, weirdly failing to start (6)
I believe the answer is:
direly
'critically' is the definition.
Both the answer and definition are adverbs.
Maybe you can see an association between them that I can't see?
'disastrously weirdly failing to start' is the wordplay.
'disastrously' is an anagram indicator (I've seen this in other clues).
'failing to start' means to remove the first letter.
'weirdly' with its first letter taken away is 'eirdly'.
'eirdly' is an anagram of 'DIRELY'.
Can you help me to learn more?
(Another definition for direly that I've seen is " urgently".)