Answer: undo

AnswerCrossword Clue
UNDOCancel
UNDOMenu option after a mistake
UNDOBring to ruin
UNDOWord-processor command
UNDOComputer function often represented by a counterclockwise arrow
UNDOLoosen, as a knot
UNDOWord processing command
UNDO"Go back," in word processing
UNDOEdit menu option
UNDONullify
UNDOBring to naught
UNDONegate
UNDOChange-of-heart word processing command
UNDOProgram's "Go back!" command
UNDORemove, as a knot
UNDODeconstruct
UNDOEdit menu choice
UNDOWord processor's "Cancel that last step"
UNDOBackspace, perhaps
UNDOBackwards-arrow command
undoruin the worldly means, reputation, or hopes of a politician undone by scandal
UNDOC--, in Emacs
UNDOErase
UNDOLoosen
UNDOReverse
UNDORub out
UNDOOpen
UNDOReverse, in a way
UNDOTake apart
UNDOTake back
UNDOPC command
UNDODisconnect
UNDOCtrl+Z command
UNDOCommand + Z command
UNDO... Send (itchy trigger finger antidote in Gmail)
UNDOComputer command
UNDOMistake maker's computer command
UNDOEdit-menu command
UNDOOpen, as a clasp
UNDOMake in reverse