This is the 17166th most frequent Russian word.
стену
"Стену" is the accusative singular form of "стена," meaning "wall" in English.
The word 'стену' here is used as a direct object in the accusative case to indicate the location of an action (painting).
Я нарисовал картину на стену.
I painted a picture on the wall.
In this sentence, 'стену' is used to show direction towards the surface (the wall) where the action (leaning) is directed.
Мы прислонили доску к стену.
We leaned the board against the wall.
Here, 'стену' functions as the object in the context of attention or gaze directed towards an entity (the wall).