Their changes add years of tradition (8)
I believe the answer is:
heritage
'tradition' is the definition.
(I've seen this before)
'their changes add years' is the wordplay.
'changes' indicates anagramming the letters.
'add' says to put letters next to each other.
'years' becomes 'age' ('age' can be a synonym of 'years').
'their' with letters rearranged gives 'herit'.
'herit'+'age'='HERITAGE'
'of' acts as a link.
(Other definitions for heritage that I've seen before include "Birth-related condition" , "Objects and cultural traditions passed down" , "Ancestry" , "Treasured historic items" , "That which is passed down by tradition" .)