Limit studies before school (9)
I believe the answer is:
constrain
'limit' is the definition.
(constraining is a kind of limiting)
'studies before school' is the wordplay.
'studies' becomes 'cons' (conning is a kind of studying).
'before' means one lot of letters go next to another.
'school' becomes 'train' (training is a kind of schooling**).
'cons'+'train'='CONSTRAIN'
(Other definitions for constrain that I've seen before include "Lock up" , "Confine, limit" , "Severely restrict" , "Compel; constrict" , "Check" .)