Portent (4)
'portent' is the definition.
(synonyms)
This is all the clue.
(Other definitions for omen that I've seen before include "Foreboding" , "Portent, prophetic sign" , "Sign of likely future event" , "Forewarning, harbinger" , "Event regarded as a prophetic sign of good or evil" .)
'portent' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sign that I've seen before include "Public notice; gesture" , "Engage by written agreement" , "Endorse" , "Indicator" , "Augury" .)