Acrobatic Ability Walkthrough
To get the Acrobatic Ability you have to talk to Moth in the circus. First he'll ask you to train with Jamie there. To cross Jamies' rope you have to take off almost all your gear. The shelves in Moth's and Jamie's rooms have permanent storage and you can store your stuff there. After you cross Jamie's rope, see Moth and he'll give you the quest to test your dexterity by crossing his tightrope and swinging on his trapeze.
You can start to cross his rope with a Dexterity level of 44 but to swing on his trapeze you'll need Dexterity of at least 78.
Go back to Moth for Acrobatic Ability reward.