One runs over different old forgotten instrument (12)
I believe the answer is:
stradivarius
'instrument' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for stradivarius that I've seen before include "Prized maker of stringed instruments" , "Pupil of Amati" , "An expensive fiddle!" , "Famous make of stringed instrument" , "Violin maker" .)