The Clock (unproduced TV story)
From Tardis Wiki, the free Doctor Who reference
The Clock was an unproduced story written by David Ellis for Season 4. The story was submitted around January 1966, and rejected by story editor Gerry Davis on 4 April 1966. (REF: Doctor Who The Handbook: The First Doctor)
A short synopsis of the story did explain that the Doctor, Polly and Ben would encounter a sinister mechanism controlling time in a disastrous result.... a clock.