Mastered Lycanthropy (5e Feat)
From D&D Wiki
You've learned to work in sync with your Lycanthropy better than normal people.
You can partially transform individual limbs into their hybrid form, allowing you to stay disguised as a normal humanoid while using your hybrid form abilities (Assuming those limbs aren't exposed). For example, you might use your claw attack while in humanoid form, transforming your arm to do so. You can also use this to benefit from your hybrid form's movement speed by transforming you legs. These transformations won't cause your equipment or clothing to meld into your form, so be aware of the potential to break your own stuff by the transformation if it is dramatically different from your normal size and shape. If an item cannot be broken easily (Such as being a magic item with Unbreakable), than you won't be able to partially transform this way without removing the item first.