Answer: unedge

AnswerCrossword Clue
UNEDGEMake dull.
UNEDGEMake dull, as a knife.
unedgeto blunt (to make dull (mentally slow))
unedgethe line at which something ends
unedgesharpness
unedgeto border
unedgethe thin, sharp side of a blade
unedgeto move gradually
unedgeverge