Secure gold in horse-drawn carriage (6)
I believe the answer is:
landau
'horse-drawn carriage' is the definition.
(I've seen this before)
'secure gold' is the wordplay.
'secure' becomes 'land' (land can mean to secure or obtain).
'gold' becomes 'au' (Au is the chemical symbol for gold).
'land'+'au'='LANDAU'
'in' acts as a link.
(Other definitions for landau that I've seen before include "Horse-drawn carriage or car with folding top" , "An auld type of carriage" , "Four-wheeled vehicle with two folding hoods" , "Transport" , "A four-wheel covered carriage" .)