UNDO is a playable word

undo Scrabble® Dictionary

undid, undone, undoing, undoes
to bring to ruin
pl. undos
a computer feature that allows the user to reverse the effect of the last action
14 Playable Words can be made from "UNDO"
   2-Letter Words (6 found)
   3-Letter Words (6 found)
   4-Letter Words (2 found)