Agricultural implement in school (6)
I believe the answer is:
harrow
This clue is a double definition.
'agricultural implement' is the first definition.
(I've seen this before)
'school' is the second definition.
(famous UK public school)
'in' is the link.
(Other definitions for harrow that I've seen before include "Soil cultivator - English public school" , "Agricultural device" , "Equipment provided for ground-breaking" , "It breaks up clods and covers seeds" , "English public school - farm implement" .)