Loud horn (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
klaxon
'loud horn' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for klaxon that I've seen before include "warning device" , "source of warning" , "Warning hooter" , "Old car horn" , "Blaring horn" .)