Where, at school, one may be out to start trouble (4)
I believe the answer is:
eton
'where at school' is the definition.
The definition suggests a singular noun which matches the answer.
'one may be out to start trouble' is the wordplay.
'may be' is an anagram indicator.
'out' indicates putting letters inside.
'to start' says to take the initial letters.
The initial letter of 'trouble' is 't'.
'one' with letters rearranged gives 'eon'.
'eon' enclosing 't' is 'ETON'.
Can you help me to learn more?
(Other definitions for eton that I've seen before include "academic institution" , "School near Slough" , "Leading English public school" , "Berkshire town" , "old school" .)