The answers to the clues below will have something in common.

1. Spotless
2. Expose corruption
3. Parent of a well-known artist
4. Seven Dwarfs' advice
5. Blowin' smoke
6. Small town, perhaps

Answers:

1. Clean as a whistle
2. Whistle-blower
3. Whistler's Mother
4. Whistle While You Work
5. Whistlin' Dixie
6. Whistle-stop 

Credit: NY Times Crossword
December 4, 1995
Sidney L. Robbins (#1-3)