a.social_media p{
  position: relative;
}
a.social_media p::after { 
  position: absolute; 
  content: ''; 
  left: 0; 
  bottom: 0; 
  display: block; 
  width: 100%; 
  height: 1px; 
  background: #fd702d;
  width: 0; 
  transition: 0.3s;
}
a.social_media:hover p:after{
  width: 100%;
}