Secure golden carriage (6)
I believe the answer is:
landau
'carriage' is the definition.
(type of horse-drawn carriage)
'secure golden' is the wordplay.
'secure' becomes 'land' (I've seen this in another clue).
'golden' becomes 'au' (Au is the chemical symbol for gold).
'land'+'au'='LANDAU'
(Other definitions for landau that I've seen before include "Four-wheeled vehicle with two folding hoods" , "Transport" , "Horse-drawn carriage or car with folding top" , "Horse-drawn, folded-top carriage" , "Four-wheeled horse-drawn carriage" .)