Nocturnal hooter (3)
I believe the answer is:
owl
'nocturnal hooter' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for owl that I've seen before include "Nocturnal bird of prey" , "Head-swivelling night bird" , "One flying" , "Bird of prey with front-facing eyes" , "Someone solemn or wise or staying up at night" .)