Unfortunate incident arose, being careless (13)
I believe the answer is:
inconsiderate
'careless' is the definition.
(I've seen this before)
'unfortunate incident arose' is the wordplay.
'unfortunate' indicates anagramming the letters.
'incident'+'arose'='incidentarose'
'incidentarose' is an anagram of 'INCONSIDERATE'.
'being' is the link.
(Other definitions for inconsiderate that I've seen before include "uncharitable" , "Thoughtless, rash" , "Lacking regard for the feelings of others" , "Unthinking" , "intolerant" .)