Vehicle was first to carry silver (5)
I believe the answer is:
wagon
'vehicle' is the definition.
(I know that wagon is a type of motor car)
'first to carry silver' is the wordplay.
'first to' becomes 'won' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'carry' is an insertion indicator.
'silver' becomes 'Ag' (Ag is the chemical symbol for silver).
'won' enclosing 'ag' is 'WAGON'.
'was' is the link.
Can you help me to learn more?
(Other definitions for wagon that I've seen before include "Wild West trail vehicle?" , "Freight truck" , "Wheeled vehicle drawn by a horse" , "Horse-drawn vehicle" , "Transport" .)