Instruct the class (5)
I believe the answer is:
order
I believe this clue is a double definition.
'instruct' is the first definition.
(to instruct is to give orders)
'class' is the second definition.
(I've seen this in another clue)
'the' is the link.
(Other definitions for order that I've seen before include "Uniformity or fraternity" , "One may be tall if demanding" , "Jesuits, say" , "Tidy state - that's a command" , "architectural style" .)