Fail to attend again? That’s careless (6)
I believe the answer is:
remiss
'careless' is the definition.
(I've seen this before)
'fail to attend again?' is the wordplay.
'fail' becomes 'miss' (missing is a kind of failing).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'attend again?' becomes 're' (I can't explain this - if you can you should give a lot more credence to this answer).
'miss' after 're' is 'REMISS'.
'that's' is the link.
Can you help me to learn more?
(Other definitions for remiss that I've seen before include "Wrong" , "Failing in one's duty" , "Negligent, slack" , "Derelict in duty" , "delinquent" .)