TASM

Set to 3 different clues across 4 published puzzles, most often “Land under Down Under: Abbr.” — The New York Times, Thursday, 21 October 2010.

4 letters

Every clue on record, most used first

Land under Down Under: Abbr.2 times
The New York Times — Thursday, 21 October 2010
Australian island: Abbr.once
The New York Times — Wednesday, 20 May 2009
Island that's part of 90-Down: Abbr.once
The New York Times — Sunday, 1 October 2006