Greyhound vehicle (3)
I believe the answer is:
bus
'greyhound vehicle' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for bus that I've seen before include "Motor-coach" , "Public service vehicle" , "Of projectiles; (go) mad (slang)" , "Mode of public transport" , "Charabanc" .)