Unfavourable (8)
'unfavourable' is the definition.
(similar in meaning)
This is all the clue.
(Other definitions for adverse that I've seen before include "In an opposing direction" , "Opposed to or unfavourable" , "Detrimental" , "Conflicting" , "Opposed - inauspicious - opposite" .)
'unfavourable' is the definition.
(similar in meaning)
This is the entire clue.
(Other definitions for untoward that I've seen before include "Unfortunate or unfavourable" , "Drawn out to be inconvenient or awkward" , "Unexpected, adverse" , "Unexpected, inappropriate" , "Inopportune" .)