Stylish graduate became firm over pupils taught together (10)
I believe the answer is:
classmates
'stylish graduate became firm' is the definition.
I can't tell whether this definition defines the answer.
'over pupils taught together' is the wordplay.
'over' means one lot of letters go next to another.
'pupils' becomes 'class' (I've seen this before).
'taught together' becomes 'mates' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'class' put next to 'mates' is 'CLASSMATES'.
Can you help me to learn more?
(Other definitions for classmates that I've seen before include "Fellow school pals" , "Pupils in the same form" , "Fellows in education" .)