Crumble gives autumn a role (4,5)
I believe the answer is:
Here is my best explanation:
'crumble' is the definition.
('fall apart' can be a synonym of 'crumble')
'autumn a role' is the subsidiary indication.
'autumn' becomes 'fall' ('fall' can be a synonym of 'autumn').
'role' becomes 'part' ('part' can be a synonym of 'role').
'gives' is the link.
(Other definitions for fall apart that I've seen before include "Go to pieces", "Come to pieces" and "Disintegrate".)