- You may be looking for the short story.
Dust or Foreman's World was a planet on the edge of the galaxy that was colonised by the Earth Empire but never fully developed. It was eventually abandoned by the Empire, leaving the colonists to fend for themselves.
In the 38th century, Dust was visited by I.M. Foreman's Travelling Show. Faction Paradox attempted to take control of Dust, but was prevented from doing so by the Third Doctor. I.M. Foreman's last incarnation was convinced to merge with the planet's biosphere, turning it into a fertile world. I.M. Foreman then renamed Dust "Foreman's World". Dust was also the location where the Third Doctor's history was changed so that he regenerated ahead of schedule, (PROSE: Interference - Book One / Interference - Book Two) but the Eighth Doctor was later able to undo the altered timeline with the aid of his TARDIS, apparently undoing his entire visit to Dust. (PROSE: The Ancestor Cell)