Unlucky over without taking duck (7)
I believe the answer is:
ominous
'unlucky' is the definition.
(thesaurus)
'without taking duck' is the wordplay.
I cannot really see how this works, but
'without' could be 'no' and 'no' is found within the answer.
'duck' could be 'o' (resembles zero - 'duck' in cricket) and 'o' is found in the answer.
This explanation may well be incorrect...
'over' is the link.
Can you help me to learn more?
(Other definitions for ominous that I've seen before include "'Threatening, foreshadowing tragedy (7)'" , "Foreboding, menacing" , "Threatening or foreshadowing evil or tragedy" , "Sinister-looking" , "Portending evil" .)