Car with old sound (5)
I believe the answer is:
audio
'sound' is the definition.
(audio means sound)
'car with old' is the wordplay.
'car' becomes 'audi' (Audi is a German car brand).
'with' says to put letters next to each other.
'old' becomes 'o' (abbreviation).
'audi'+'o'='AUDIO'
(Other definitions for audio that I've seen before include "Acoustic reproduction" , "Car" , "- - visual aids" , "Electronic sound reproduction" , "Sound broadcast" .)