Teacher has said no running around for new students (10)
I believe the answer is:
admissions
'new students' is the definition.
Although both the answer and definition are plural nouns, I can't see how they can define each other.
'teacher has said no running around' is the wordplay.
'teacher has' becomes 'miss' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'running' indicates anagramming the letters (the letters run around to different places).
'around' means one lot of letters goes inside another.
'said'+'no'='saidno'
'saidno' with letters rearranged gives 'adions'.
'miss' going within 'adions' is 'ADMISSIONS'.
'for' is the link.
Can you help me to learn more?
(Other definitions for admissions that I've seen before include "Costs of entering" , "Acknowledgments" .)