The most common and most likely answer to this crossword clue is the 9 letter word MERCAPTAN
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More clues leading to the result MERCAPTAN
Buddy explains!
The straight part
We know that "Chemical compound" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case chemical compound = mercaptan.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 MERCAPTAN mean?
MERCAPTAN noun- Any of a class of organic compounds of sulphur, ( R1.S.R2 ); they tend to be foul-smelling. When R2 is a hydrogen atom, they are termed thiols or thioalcohols.