Klaxon (4)
'klaxon' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for hooter that I've seen before include "Siren, steam whistle" , "Uphill stone pusher (Gk. myth)" , "Car horn or slang nose" , "It makes a loud noise" , "Siren, horn; nose" .)
'klaxon' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for horn that I've seen before include "Musical instrument - antler" , "Hooter" , "Bony outgrowth on an animal" , "Brass musical instrument" , "See 1 Across" .)