Command of a class? (5)
I believe the answer is:
order
I believe this is a double definition.
'command' is the first definition.
(I know that order is a type of command)
'a class?' is the second definition.
(I've seen this before)
'of' is the link.
(Other definitions for order that I've seen before include "Instruction - arrangement" , "Instruct" , "Symmetry" , "Family - group - arrangement" , "Tidy and settled condition" .)