The most common and most likely answer to this crossword clue is the 9 letter word FATHOMING
I've seen this crossword clue in The Times
F
A
T
H
O
M
I
N
G
Buddy explains!

The straight part
We know that "working out" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case working out = fathoming.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 FATHOMING mean?
FATHOMING verb- To encircle with outstretched arms, especially to take a measurement; to embrace.
- To measure the depth of, take a sounding of.
- To get to the bottom of; to manage to comprehend; understand (a problem etc.).