They fall annually (6)
I believe the answer is:
leaves
'they' is the definition.
Both the definition and answer are plural nouns.
Maybe they are linked in a way I don't understand?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for leaves that I've seen before include "They are found on trees and in books" , "See 14" , "Departs with what fall in the Fall" , "''... of Grass'' (Walt Whitman)" , "Foliage - goes away" .)