The most common and most likely answer to this crossword clue is the 9 letter word ABSCISSAS
I've seen this crossword clue in The Guardian
A
B
S
C
I
S
S
A
S
Buddy explains!

The straight part
We know that "co-ordinate values /co-ordinate values" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case co-ordinate values /co-ordinate values = abscissas.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 ABSCISSAS mean?
ABSCISSAS noun- The first of the two terms by which a point is referred to, in a system of fixed rectilinear coordinate (Cartesian coordinate) axes.
- The horizontal line representing an axis of a Cartesian coordinate system, on which the abscissa (sense above) is shown.