Unpropitious (7)
I believe the answer is:
adverse
'unpropitious' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for adverse that I've seen before include "Contrary, harmful" , "'Contrary, untoward (7)'" , "Unfavourable or harmful, perhaps criticism" , "'Unfavourable, contrary (7)'" , "Detrimental" .)