Still an imbalance expressed ahead of overhaul (7)

I believe the answer is:

alembic

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'still' is the definition.
(I know that alembic is a type of still)

I cannot understand how the rest of the clue works.

(Other definitions for alembic that I've seen before include "Still" , "Old distillation vessel" , "Old retort" .)

I've seen this clue in The Guardian.

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