Clairvoyance is a Prowess, this special kind of Feat is an action that can only be done once per scenario.
To acquire it, you need to already have another Feat related to it, for example : Eye for Detail, Physiognomist, Instinct or Photographic Memory
Your Game Master may accept to waive such prerequisites if your background or in game actions justify it.
Unlike normal Feats, a Prowess can be acquired several times.
Your are blessed with a temporary insight in your environment.
You temporarily gain the Eye for Detail, Physiognomist and Photographic Memory Feats and you gain instinctive knowledge of anything of interest in the room.
This Prowess can allow you to see any hidden objects, secret passages or perfectly concealed clues.