Cousin under threat called out hosts with a note (9)
I believe the answer is:
orangutan
'cousin under threat' is the definition.
(endangered cousin of humanity)
'called out hosts with a note' is the wordplay.
I cannot really understand how this works, but
'called' could be 'rang' ('ring' can be a synonym of 'call') and 'rang' is present in the answer.
'a' could be 'an' and 'an' is found within the answer.
'note' could be 'ut' (I've seen this in other clues) and 'ut' is present in the answer.
A single letter 'o' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
(Other definitions for orangutan that I've seen before include "a big sub-human creature" , "Primate" , "ape" .)