I know it increases the duration of Reflect and Light Screen, but what about Lucky Chant and Safeguard?
No, light clay will not increase the duration of lucky chant or safeguard. It will only increase the length of light screen and reflect from 5 to 8 turns.
No, the Light Clay only effects the duration of Reflect and Light Screen.
> If the holder uses either Light Screen or Reflect, the two moves will stay on the field for eight turns instead of five.