Rush scoundrel into trial (7)
I believe the answer is:
cascade
'rush' is the definition.
(thesaurus)
'scoundrel into trial' is the wordplay.
'scoundrel' becomes 'cad' (cad is a kind of scoundrel).
'into' indicates putting letters inside.
'trial' becomes 'case' (I've seen this in other clues).
'cad' going within 'case' is 'CASCADE'.
(Other definitions for cascade that I've seen before include "Rush" , "Sudden downpour" , "falls in the river" , "Torrent" , "Series of small waterfalls" .)