Rogue in trial falls (7)
I believe the answer is:
cascade
'falls' is the definition.
('cascade' can be a synonym of 'falls')
'rogue in trial' is the wordplay.
'rogue' becomes 'cad' (I've seen this before).
'in' means one lot of letters goes inside another.
'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 "Dramatic fall" , "Rush" , "Waterfall or deluge" , "Torrent" , "Sudden downpour" .)