It might be a bad sign (4)
I believe the answer is:
omen
'it might be a bad sign' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for omen that I've seen before include "Sign of something to come" , "writing on the wall" , "Forewarning, harbinger" , "Portent of evil" , "Harbinger, augury" .)