Defar, the 2007 world champion, starts as favourite for a second title in the absence of her great rival and compatriot Tirunesh Dibaba, who won the 10,000 crown on Sunday before saying she would not run the shorter distance.
Champion from Daegu two years ago, Vivian Cheruiyot of Kenya is also absent as she is expecting her first child.
With no evening session, the men's 50km walk will be the only medal to be decided and the hosts will have high hopes of another gold from 2009 world champion and Olympic winner Sergey Kirdyapkin.
Key times on day three (UK times)
05:30 06:30 Men's 50 Kilometres Race Walk - Final
06:30 07:30 Women's Hammer Throw - Qualification Group A
06:40 07:40 Women's 5000 Metres - Heats
07:25 08:25 Men's Long Jump - Qualification
07:35 08:35 Men's 1500 Metres - Heats
08:10 09:10 Women's Hammer Throw - Qualification Group B