Imitate an owl (4)
I believe the answer is:
hoot
'imitate an owl' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for hoot that I've seen before include "noise made by 7 [WOOD-OWL]" , "Warning sound - something not given by the careless!" , "Owlish cry" , "Cry of owl" , "Sound of owl" .)