The most common and most likely answer to this crossword clue is the 9 letter word CLOSENESS
I've seen this crossword clue in The Guardian
C
L
O
S
E
N
E
S
S
Buddy explains!

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 CLOSENESS mean?
CLOSENESS noun- The state of being close (all senses)
- The state of being friends
- The state of being mean or stingy
- The state of being secretive
- The shortest path between two vertices in a graph
- Solitude, seclusion