The most common and most likely answer to this crossword clue is the 9 letter word SULPHATES
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The cryptic/wordplay part
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Crossword Answer definitions
SULPHATES noun- Any ester of sulfuric acid.
- Any salt of sulfuric acid.
- To treat something with sulfuric acid, a sulfate, or with sulfur dioxide.
- (of a lead-acid battery) To accumulate a deposit of lead sulfate.