Answer:
The contact clue that is most helpful in determining the meaning of the word NICHE is [recess].
Step-by-step explanation:
The word recess can have different meaning depending on the context, in this sentence the word recess uses the meaning of hole or cavity, the meaning can be deduced also for the preposition "in" when they mention the old cupboard "in" the wall, which means it was inside it like a cavity not "on" it as a piece of furniture.