The phrase "mucked around" generally implies a lack of focus, purpose, or seriousness. So antonyms for this phrase might include "focused," "serious," "purposeful," "dedicated," "efficient," "responsible," or "productive." Rather than wasting time or being directionless, these words connote intention and action towards a particular goal or outcome. Additionally, antonyms for "mucked around" might include more playful or carefree terms such as "relaxed," "playful," "joyful," or "curious." Overall, antonyms for "mucked around" would encompass a range of words that emphasize focus, effort, and greater purpose in comparison to aimlessness and lack of purpose.