I'd like to revive this post for those who might come across it by chance. Here is my solution:

.vecteur {
  position: relative;
}
.vecteur::before {
  content: "\2192";
  position: absolute;
  top: -0.7em;
  left: -0.1em;
  font-size: 1.2em;
}
</style>

<span class="vecteur">a</span>