The most common and most likely answer to this crossword clue is the 13 letter word PROSTAGLANDIN
I've seen this crossword clue in The Times
P
R
O
S
T
A
G
L
A
N
D
I
N
Buddy explains!

The straight part
We know that "compound" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case compound = prostaglandin.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 PROSTAGLANDIN mean?
PROSTAGLANDIN noun- Any of a group of naturally occurring lipids derived from the C20 acid prostanoic acid; they have a number of physiological functions and may be considered to be hormones.