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"sharpen" is also used as a crossword clue. If that's what you saw, the answer is often whet (4 letters).
Definitions
put (an image) into focus
Word origin
From Middle English scharpenen, scharpnen, equivalent to sharp + -en.
Used in a sentence
“to sharpen a pencil or a knife or a musical note”
“He that wrestles with us strengthens our nerves and sharpens our skill.”
Source: Wiktionary, CC BY-SA 4.0
Used as a crossword answer1 curated clues
01“Make less dull”7 letters
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