The most common and most likely answer to this crossword clue is the 11 letter word COTERMINOUS
I've seen this crossword clue in The Times
C
O
T
E
R
M
I
N
O
U
S
Buddy explains!

The straight part
We know that "covering the same area" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case covering the same area = coterminous.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does COTERMINOUS mean?
COTERMINOUS adjective- Meeting end to end or at the ends.
- Having matching boundaries; or, adjoining and sharing a boundary.
- Having the same scope, range of meaning, or extent in time.
- Said of linked or related property leases that expire together.