Note lawsuit's response (8)
I believe the answer is:
reaction
'response' is the definition.
('reaction' can be a synonym of 'response')
'note lawsuit's' is the wordplay.
'note' becomes 're'.
'lawsuit' becomes 'action' ('action' can be a synonym of 'lawsuit').
're'+'action'='REACTION'
(Other definitions for reaction that I've seen before include "Reflex; backlash" , "Chemical change or response" , "effect of drugs?" , "Force" , "Answer" .)