Upland areas turned over after endless fighting - one should find a lesson here (9)
I believe the answer is:
classroom
'upland areas turned over after endless fighting one should find a lesson here' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'lesson here' is the wordplay.
'lesson' becomes 'class' (synonyms).
'here' becomes 'room' (I am not sure about this - if you are sure you should believe this answer much more).
'class'+'room'='CLASSROOM'
Can you help me to learn more?
(Other definitions for classroom that I've seen before include "School space" , "place of education" , "Teaching space" , "Part of a school" , "Place for lessons" .)