From Longman Dictionary of Contemporary Englishstart back phrasal verbto begin returning to the place you came from to/down/up etc I started back down the mountain to camp. → start→ See Verb table
Examples from the Corpus
start back• Frank said we should start back.• Giving the still busy Josh a parting wave, the two of them started back.• He caressed her and then he started back.• Susan saw him come out of the door and start back down the track, anger and anxiety making him push his pace.• I took a fresh notebook from the glove compartment and started back to talk to them.• But before he could move there was a click and Doyle was starting back towards the camera.• I return the papers to their envelope and start back up toward the cabin.start to/down/up etc• Lucia started backing up her books with a free hand. 