The 50-year-old woman was walking along Tewksbury Road towards Oxford Road at around 5pm on June 11 when she was approached by a man on a silver and black bicycle.
He demanded her handbag and pushed her to the floor once she refused to hand it over. The suspect then produced a knife before being disturbed by a passing motorist who shouted. He rode away on his bicycle.
The suspect was described as black and with dreadlocks.
Enquiries are ongoing and officers are keen to trace the motorist who intervened. They may have been driving a dark mini.
Anyone with information is asked to contact Ds Tim Coyles at Clacton CID on 101 or Crimestoppers, anonymously, on 0800 555 111.