Not keeping up to date with rent's said to be bad (9)
I believe the answer is:
tardiness
'not keeping up to date' is the definition.
(being tardy or delayed)
'with rent's said to be bad' is the wordplay.
'with' is a charade indicator (letters next to each other).
'to be bad' is an anagram indicator (I've seen 'being bad' mean this).
'rents' put next to 'said' is 'rentssaid'.
'rentssaid' is an anagram of 'TARDINESS'.
(Other definitions for tardiness that I've seen before include "Lateness" , "Delay" , "Habit of being late" , "No quality in fast food" , "Becoming late" .)