Shortage after Society is careless (5)
I believe the answer is:
slack
'careless' is the definition.
('slack' can be a synonym of 'careless')
'shortage after society' is the wordplay.
'shortage' becomes 'lack' (I've seen this before).
'after' means one lot of letters go next to another.
'society' becomes 's' (common abbreviation in names of organisations).
'lack' after 's' is 'SLACK'.
'is' is the link.
(Other definitions for slack that I've seen before include "skive" , "Limp - negligent" , "Flaccid" , "Not taut" , "Idle and disinclined to work" .)