Is this your crossword clue?
"sincerely" is also used as a crossword clue. If that's what you saw, the answer is often earnestly (9 letters).
Definitions
written formula for ending a letter
Word origin
From sincere + -ly, from Latin sincērus (“pure, clean, sound”).
Used in a sentence
“I sincerely hope they make it home safely.”
“Please consider the proposal carefully and let me know what you decide. Sincerely, Fred”
Source: Wiktionary, CC BY-SA 4.0
Used as a crossword answer2 curated clues
01“Letter closer”9 letters
02“Yours truly opener”9 letters
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