Heehaw (4)
I believe the answer is:
bray
'heehaw' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bray that I've seen before include "Sound asinine" , "time-serving vicar's parish" , "Donkey's call; its vicar trimmed" , "Donkey's heehaw" , "Ass's cry" .)