The most common and most likely answer to this crossword clue is the 8 letter word ANDROGEN
I've seen this crossword clue in Independent
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More clues leading to the result ANDROGEN
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The straight part
We know that "sex hormone" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sex hormone = androgen.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 ANDROGEN mean?
ANDROGEN noun- The generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of masculine characteristics in vertebrates. A male sex hormone such as testosterone or anabolic steroids.