Division of school hard by river (5)
I believe the answer is:
house
'division of school' is the definition.
(as in school houses)
'hard by river' is the wordplay.
'hard' becomes 'h' (abbreviation used in pencil classifications).
'by' says to put letters next to each other.
'river' becomes 'ouse' (Yorkshire river).
'h'+'ouse'='HOUSE'
(Other definitions for house that I've seen before include "Dwelling or official assembly" , "Domestic building" , "Building for dwelling in" , "See 18" , "Residence, dwelling" .)