Beyond the prime (8)
I believe the answer is:
autumnal
'beyond the prime' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for autumnal that I've seen before include "in a particular part of the year" , "Past the prime of growth" , "Characteristic of the fall" , "Leaves to go at such time" , "Late in the year" .)