Journey's end sealed by sound of horn on a car (6)
I believe the answer is:
toyota
'car' is the definition.
(I've seen this before)
'journey's end sealed by sound of horn on a' is the wordplay.
'end' indicates one should take the final letters.
'sealed by' indicates putting letters inside.
'sound of horn' becomes 'toot'.
'on' means one lot of letters go next to another.
The last letter of 'journey' is 'y'.
'y' inserted inside 'toot' is 'toyot'.
'toyot'+'a'='TOYOTA'
(Other definitions for toyota that I've seen before include "vehicle?" , "Japanese car maker" , "Turn to a toy for a car maker" , "Car manufacturer" , "Japanese car firm" .)