Spotted a careless mark with a later day (8)
I believe the answer is:
postdate
'day' is the definition.
(thesaurus)
'spotted a careless' is the wordplay.
'careless' indicates an anagram.
'spotted'+'a'='spotteda'
'spotteda' is an anagram of 'POSTDATE'.
'mark with a later' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for postdate that I've seen before include "Mark with a time still in the future" , "Stop immediate use of" , "Ascribe later day to" , "As potted (anag)" , "Occur later in time than" .)