Misers may become careless (6)
I believe the answer is:
remiss
'careless' is the definition.
(I know that careless can be written as remiss)
'misers may become' is the wordplay.
'may become' is an anagram indicator.
'misers' with letters rearranged gives 'REMISS'.
(Other definitions for remiss that I've seen before include "Negligent, derelict" , "Negligent, lax" , "Lacking care to duty" , "Derelict in duty" , "delinquent" .)