Attack, alas, is going wrong (6)
I believe the answer is:
assail
'attack' is the definition.
(synonyms)
'alas is going wrong' is the wordplay.
'going wrong' indicates anagramming the letters.
'alas'+'is'='alasis'
'alasis' with letters rearranged gives 'ASSAIL'.
(Other definitions for assail that I've seen before include "Make violent attack on" , "Set upon" , "Trouble" , "Beset" , "Attack violently and persistently" .)