Bellowing (5)
'bellowing' is the definition.
(I know that bellowing can be written as roaring)
This is the entire clue.
(Other definitions for roaring that I've seen before include "& 1 Across Strong winds in S. Hemisphere" , "Bellowing, hollering" , "Sounding as a lion" , "Emphatic (success)" , "Making cry (like a lion)" .)