All the pupils perhaps greet sir in order (8)
I believe the answer is:
register
'all the pupils' is the definition.
I can't judge whether this definition defines the answer.
'greet sir in order' is the wordplay.
'in order' is an anagram indicator (the letters in a new order).
'greet'+'sir'='greetsir'
'greetsir' with letters rearranged gives 'REGISTER'.
'perhaps' is the link.
Can you help me to learn more?
(Other definitions for register that I've seen before include "Official list or record" , "To express" , "New arrival at hotel will" , "Written record of names, etc" , "part of our paper" .)