A repair shop was a shop where broken or faulty items could be taken in and repaired.
There was a repair shop in the Citadel of the Time Lords on Gallifrey, among the items there were TARDISes. Two technicians, Andro and Fabian, were working there when the First Doctor, with his granddaughter, stole a faulty Type 40 TARDIS. (TV: The Name of the Doctor)
The Third Doctor owned a watch-mending shop called Fixing Time, on Old Street, Islington, London. After he refused to pay protection money to the Ramsey Mob, Jack Cooper, a member of the mob, torched the place. (PROSE: Amorality Tale)