The most common and most likely answer to this crossword clue is the 9 letter word SCIENTISM
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Buddy explains!
The straight part
We know that "treating biology etc, as all-important" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case treating biology etc, as all-important = scientism.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.
Crossword Answer definitions
SCIENTISM noun- The belief that the scientific method and the assumptions and research methods of the physical sciences are applicable to all other disciplines (such as the humanities and social sciences), or that those other disciplines are not as valuable.
- The belief that all truth is exclusively discovered through science.