Beastly noises from the spectators (5)
I believe the answer is:
roars
'beastly noises' is the definition.
'roars' can be an answer for 'noises' (roaring is a kind of noising). I am not certain of the 'beastly' bit.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for roars that I've seen before include "Sounds like a lion" , "Calls like lion" , "Deep bellows" , "Bellows, hollers" , "Bellows like a bull" .)