Hostility as I am surrounded by a group of students (6)
I believe the answer is:
animus
'hostility' is the definition.
(I know that animus is a type of hostility)
'i am surrounded by a group of students' is the wordplay.
'i am' becomes 'I'm' (contraction).
'surrounded by' is an insertion indicator.
'group of students' becomes 'NUS' (National Union of Students).
'a'+'nus'='anus'
'im' placed into 'anus' is 'ANIMUS'.
'as' acts as a link.
(Other definitions for animus that I've seen before include "Motivating spirit" , "Feeling of strong dislike" , "Bad blood" , "A feeling of ill will or hostility" , "Hostility, ill-feeling" .)