Not the whole area (3)
I believe the answer is:
are
'area' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for are that I've seen before include "is for more than one" , "(We/you/they) exist" , "live" , "Unit of land measure equal to 100 square metres" , "Exist; square measure" .)