Last short epistle used in university, after appropriate period (8)
I believe the answer is:
ultimate
'last' is the definition.
('ultimate' can be similar in meaning to 'last')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for ultimate that I've seen before include "Best or most extreme" , "Happening at the end of a process, final" , "Best - last" , "Final; fundamental" , "Utmost or extreme" .)