Fall of rotter involved in lawsuit (7)
I believe the answer is:
cascade
'fall' is the definition.
(cascading is a kind of falling)
'rotter involved in lawsuit' is the wordplay.
'rotter' becomes 'cad' (I've seen this before).
'involved in' indicates putting letters inside.
'lawsuit' becomes 'case' ('case' can be a synonym of 'lawsuit').
'cad' going into 'case' is 'CASCADE'.
'of' is the link.
(Other definitions for cascade that I've seen before include "Series of small waterfalls" , "Tumble down (like water)" , "Sudden downpour" , "Rush" , "Small waterfall or series of them" .)