Wrong about good omen (4)
I believe the answer is:
sign
'omen' is the definition.
(I've seen this before)
'wrong about good' is the wordplay.
'wrong' becomes 'sin' (I've seen this in another clue).
'about' indicates putting letters inside.
'good' becomes 'g' (abbreviation).
'sin' going around 'g' is 'SIGN'.
(Other definitions for sign that I've seen before include "As the star was for 14 across" , "Omen or indication" , "add name" , "Show" , "Engage by written agreement" .)