Division of a school year (4)
I believe the answer is:
term
'division of a school year' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for term that I've seen before include "what being 9 [PREGNANT] leads to?" , "Period of education" , "Call" , "Expression, or school period" , "Word; limited period" .)