“Gel” as a New York Times crossword clue is most often answered as:

• COALESCE (especially in recent full-size NYT Crosswords, meaning “come together” or “blend”)

• SET (a common shorter answer, especially in earlier or non-themeless puzzles, meaning “to firm up”)

If you have a specific puzzle date, grid length, or some crossing letters, that can narrow which of these (or another synonym) is correct for your particular NYT crossword.