Time for school? (3)
I believe the answer is:
day
This clue is a double definition.
'time' is the first definition.
(day is a kind of time)
'school?' is the second definition.
(day school is a kind of school)
'for' is the link.
(Other definitions for day that I've seen before include "Born yesterday" , "24 hour period" , "Lewis as poet" , "Particular date" , "THIRD PART OF 23" .)