If internship is still ahead of you, do everything possible to finish the dissertation before internship. It allows you to really make the most of the internship year. (And it is a great advantage in the Match.)
However if not done yet when finishing internship, taking time to focus and finish it makes you a stronger job candidate, so I'd say power through it full time unless you have an irresistible job offer and the employer is not anxious to have you licensed. Clinical work is challenging and distracting and it will prolong the completion.