Howling (6)
'howling' is the definition.
('roar' can be a synonym of 'howl')
This is all the clue.
(Other definitions for roaring that I've seen before include "& 1 Across Strong winds in S. Hemisphere" , "Making cry (like a lion)" , "The Lion's part, nothing but this (MND)" , "Emphatic (success)" , "Do a - trade, - forties" .)
(Other definitions for baying that I've seen before include "The sound of hounds in pursuit" , "Barking with prolonged noises" , "Howling like a dog" .)