Three Letters:
* era
* art
* tar
* rat
* tan
* ant
* tin
* ton
* din
* don
* ran
* ray
* try
* dry
*
Four Letters:
* rain
* rant
* torn
* road
* riot
* dart
* tray
* riot
* iron
* done
Five Letters:
* train
* drain
* roar
* story
* order
* adore
* adore
* radio
* tenor
* drone
* trant
* trany
Six Letters:
* ordinary
* ordain
* doting
* trantor
* rattan
Seven Letters:
* ordinary
* extra
* radios
Eight Letters:
* extraordinary
This list isn't exhaustive, and there may be other words depending on the specific word game rules.