Violent, tempestuous (6)
I believe the answer is:
raging
I believe this clue is a double definition.
'violent' is the first definition.
(I've seen this in another clue)
'tempestuous' is the second definition.
(I know that tempestuous can be written as raging)
(Other definitions for raging that I've seen before include "Expressing violent anger" , ". . . . . . Bull (Martin Scorsese film)" , "Showing violent anger" , "Furious as storm may be" , "(Of fire or storm) violent" .)