Auto installation (6)
I believe the answer is:
stereo
'auto installation' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stereo that I've seen before include "One might play record" , "Sound transmission from two sources through two channels" , "Sound coming from different directions" , "System of sound reproduction" , "Sound transmission through two or more speakers" .)