Attack a lass I converted (6)
I believe the answer is:
assail
'attack' is the definition.
(I know that attack can be written as assail)
'a lass i converted' is the wordplay.
'converted' indicates anagramming the letters.
'lass'+'i'='lassi'
'lassi' with letters rearranged gives 'ssail'.
'a'+'ssail'='ASSAIL'
(Other definitions for assail that I've seen before include "Make violent attack on" , "Slate" , "storm" , "Aggressively attack" , "Attack violently and persistently" .)