The most common and most likely answer to this crossword clue is the 9 letter word MODERATES
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More clues leading to the result MODERATES
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The straight part
We know that "Restrains" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case restrains = moderates.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 MODERATES mean?
MODERATES noun- One who holds an intermediate position between extremes, as in politics.
- One of a party in Scottish Church history dominant in the 18th century, lax in doctrine and discipline, but intolerant of evangelicalism and popular rights. It caused the secessions of 1733 and 1761, and its final resultant was the Disruption of 1843.