A scream (7)
I believe the answer is:
riotous
'a scream' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for riotous that I've seen before include "Unruly U rebellious" , "Wild, disorderly" , "Boisterous and unrestrained" , "Wild, uncontrolled" , "Unrestrained, wild living perhaps" .)