Give the character a power action. Place a thwart token on a target feat card assigned to a character that is 10 or fewer squares from the character and to which the character has a clear line of fire. The target feat is ignored until a character to which it is assigned is given a power action specifically to remove the thwart token. What does it mean 'given a power action specifically to remove the thwart token' ? What exactly do you have to do?

The character who was 'thwarted' just has to get an action token(DOING nothing) to remove the token on their feat card. Just like giving a character a power action to get a power from Oracle when she's on her card. Make sense?