School working at hit crime novel (10)
I believe the answer is:
arithmetic
'school working' is the definition.
The answer and definition can be both related to thinking as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'at hit crime novel' is the wordplay.
'novel' indicates an anagram.
'at'+'hit'+'crime'='athitcrime'
'athitcrime' is an anagram of 'ARITHMETIC'.
Can you help me to learn more?
(Other definitions for arithmetic that I've seen before include "School subject" , "Numerical calculations" , "Branch of mathematics" , "kind of mean" , "Calculation" .)