This feature is available in all editions
Why don't acceptance tests on a Defect or Test Set have a Detail Estimate?
Acceptance tests (also called tests) that are associated with a story/backlog item have a Detail Estimate, but those associated with Defects or Test Sets do not.
What you can do
Backlog Items and Defects
The ability to configure tracking levels is only available in Enterprise and Ultimate editions.
Default Tracking Levels
The default tracking level for a story is at the Task/Test level. You can enter detail estimate, to do, and effort (done) on tasks and tests, and the values roll up to the story. The default tracking level for a defect is at the default Defect level. You can enter detail estimate, to do, and effort (done) on the defect. In order to Track at the Task/Test level you will need to adjust the Tracking Level to tasks and tests.
With Catalyst Edition, Tracking is configured at the Defect level only. For the ability to Track at a child Task/Test level of a Defect, you will need to upgrade to Enterprise Edition or higher.
Test Sets do not have the same configuration capability. Currently, the tracking level for Test Sets is at the Testset level only, so you cannot enter detail estimate, to do, or effort (done) for tests in a Test Set. In our backlog for regression testing, we have a Backlog Item for adding that same configuration capability on Test Sets. Please visit IdeaSpace and comment on related ideas.