Edgy student hides discomfort when given envelope (6)
I believe the answer is:
sachet
'envelope' is the definition.
(I have seen 'Small envelope ' mean 'sachet' so perhaps 'envelope' could also mean 'sachet')
'edgy student hides discomfort' is the wordplay.
'edgy student' becomes 'st' (I can't explain this - if you can you should give a lot more credence to this answer).
'hides' means one lot of letters goes inside another.
'discomfort' becomes 'ache' (I've seen this in another clue).
'st' going around 'ache' is 'SACHET'.
'when given' is the link.
Can you help me to learn more?
(Other definitions for sachet that I've seen before include "Cheats (anag) -- small porous bag" , "Small bag or packet" , "Package" , "Scent bag - shampoo envelope" , "Small sealed packet" .)