Greek bird making beastly noise (5)
I believe the answer is:
growl
'beastly noise' is the definition.
The answer and definition can be both related to natural events as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'greek bird' is the wordplay.
'greek' becomes 'gr' (abbreviation for Greek).
'bird' becomes 'owl' (owl is a kind of bird).
'gr'+'owl'='GROWL'
'making' is the link.
Can you help me to learn more?
(Other definitions for growl that I've seen before include "Make an aggressive sound" , "Emit low rumbling sounds" , "Noise of an angry dog" , "warn of attack" , "Low rumble" .)