The crossword clue "hollow" can have various answers depending on the number of letters required by the puzzle. Common answers include:

• 3 letters: DEN, DIP, PIT
• 4 letters: DENT, VALE, DALE, DELL, CAVE, GLEN
• 5 letters: EMPTY, SINUS
• 6 letters: CAVITY, RAVINE, SUNKEN
• 7 letters: CONCAVE

The most frequent and likely 4-letter answer is "DENT," but others like VALE, DALE, and CAVE are also common. For shorter clues, "DEN" or "PIT" works well, while longer clues can be "CAVITY" or "RAVINE." The answer depends on the letter count and intersecting letters in the specific crossword puzzle.