The most common and most likely answer to this crossword clue is the 8 letter word ISOSTASY
I've seen this crossword clue in Financial Times
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More clues leading to the result ISOSTASY
- Excluding me, some say it’s altered earth’s equilibrium
- State of equilibrium is upset, so son falls in river
- I call for help and stay working for balanced state
- Assist artfully, catching ball close to boundary showing equilibrium
- . Geological equilibrium is zero, stays in order
- Geological equilibrium, say — it's so unstable
- Very boring, say it’s sort of geological equilibrium
- I call for help — Yankee sat back in balanced state
Buddy explains!

The straight part
We know that "State of equilibrium" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case state of equilibrium = isostasy.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 ISOSTASY mean?
ISOSTASY noun- The state of balance or pressure equilibrium thought to exist within the Earth's crust, whereby the upper lithosphere floats on denser magma beneath.