Closing university email messed about time and time again (8)
I believe the answer is:
ultimate
'closing university email' is the definition.
'ultimate' can be an answer for 'closing' (thesaurus). I am not certain of the 'university email' bit.
'messed about time and time again' is the wordplay.
'messed' is an anagram indicator (I've seen this in other clues).
'about' becomes 'a' (abbreviation in Chambers).
'and' is a charade indicator (letters next to each other).
'time again' becomes 'ult' (I can't explain this - if you can you should believe this answer much more).
'a'+'time'='atime'
'atime' anagrammed gives 'imate'.
'imate' put after 'ult' is 'ULTIMATE'.
(Other definitions for ultimate that I've seen before include "Mutilate in final way" , "Eventual" , "Happening at the end of a process, final" , "The final point" , "Final; fundamental" .)