in a cast

“Sita has recovered after the accident, but her fractured arm is still in a cast.”
Please correct it.
What is the meaning for ‘in a cast’?

The sentence is correct.

“cast” is sense 6c at :

“a rigid casing (as of fiberglass or of gauze impregnated with plaster of paris) used for immobilizing a usually diseased or broken part”