Unofficial instruction to tell a student what is going on (8)
I believe the answer is:
informal
'unofficial' is the definition.
('informal' can be similar in meaning to 'unofficial')
'a student what is going on' is the wordplay.
'student' becomes 'l'.
'what' becomes 'inform' (I can't justify this - if you can you should believe this answer much more).
'is going on' says to put letters next to each other.
'a'+'l'='al'
'al' put after 'inform' is 'INFORMAL'.
'instruction to tell' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for informal that I've seen before include "Cosy -- loose" , "Casual, not official" , "If normal, be casual and without ceremony" , "Unofficial, relaxed" , "Casual, free and easy" .)