Light gold carriage (6)
I believe the answer is:
landau
'carriage' is the definition.
(I've seen this before)
'light gold' is the wordplay.
'light' becomes 'land' (I've seen this before).
'gold' becomes 'au' (Au is the chemical symbol for gold**).
'land'+'au'='LANDAU'
(Other definitions for landau that I've seen before include "Transport" , "An auld type of carriage" , "A four-wheel covered carriage" , "Four-wheeled horse-drawn carriage" , "Horse-drawn carriage or car with folding top" .)