Part of core curriculum to come up again (5)
I believe the answer is:
recur
'come up again' is the definition.
(to recur is to appear or come up again)
'part of core curriculum to' is the wordplay.
'part of' indicates the answer is hidden within the clue.
'RECUR' is hidden within 'core curriculum to'.
(Other definitions for recur that I've seen before include "Repeat" , "Be repeated" , "Happen again or repetitively" , "Return to mind" , "Come round again" .)