.area{
  font-size: 20px;
  display: inline-block;
  background: green;
  padding: 20px;
  border: 4px;
  position: relative;
  cursor: pointer;
}
span{
  position: relative;
  z-index: 1;
}
.area::after{
  content: '';
  position: absolute;
  right: 0;
  top: 0;
  background-color: yellow;
  width: 100%;
  height: 100%;
  clip-path: circle(0% at 0% 0%);
  transition: all 1s ease;
  z-index: 0;
}
.area:hover::after{
   clip-path: circle(200% at 0% 0%);
}