The most common and most likely answer to this crossword clue is the 5 letter word AZOIC
I've seen this crossword clue in Independent
A
Z
O
I
C
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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 AZOIC mean?
AZOIC adjective- Destitute of any vestige of organic life, or at least of animal life
- Anterior to the existence of animal life
- Formed when there was no animal life on the globe