Vehicle air-conditioning turned on, heading for Rye (3)
I believe the answer is:
car
'vehicle' is the definition.
(car is a kind of vehicle)
'air-conditioning turned on heading for rye' is the wordplay.
'air conditioning' becomes 'AC'.
'turned' says the letters should be written backwards.
'on' is a charade indicator (letters next to each other).
'heading for' indicates taking the first letters.
The initial letter of 'rye' is 'r'.
'ac' back-to-front is 'ca'.
'ca'+'r'='CAR'
(Other definitions for car that I've seen before include "Motor vehicle" , "Vehicle carrying vehicles" , "Wheels" , "Personal vehicle" , "4-wheeled vehicle" .)