It's a bad thing to be overthrown (4)
I believe the answer is:
evil
'it's a bad thing' is the definition.
(I've seen this in another clue)
'be overthrown' is the wordplay.
'be' becomes 'live' (to be is to live or exist).
'overthrown' says the letters should be written backwards.
'live' backwards is 'EVIL'.
'to' acts as a link.
(Other definitions for evil that I've seen before include "no good in this puzzle" , "Extremely wicked" , "Wicked - social problem" , "A live sort of badness" , "Morally objectionable behavior" .)