LACTOSE

Set to 3 different clues across 3 published puzzles, most often “Cause of some intolerance” — The New York Times, Sunday, 21 September 2003.

7 letters

Every clue on record, most used first

Cause of some intoleranceonce
The New York Times — Sunday, 21 September 2003
Source of intoleranceonce
The New York Times — Thursday, 29 April 1999
What some folks can't tolerateonce
The New York Times — Wednesday, 31 December 1997