It's job is to make you hold water so your muscle cells are full. Helps with ATP so that energy transfer across cells is better. In the end of a long scientific discussion which I hate and wont get into...it helps make you a little stronger.
Stronger means you lift more.
You lift more you build more muscle.
You build more muscle you need more calories to maintain it - automatically creating a
caloric deficit.
This deficit = fat loss.
So actually, the extra water in your cells kind of indirectly helps with fat loss...if you are busting your butt in the gym and have nutrition & cardio dialed in along with the lifting plan.
Be sure to drink more water if you are on creatine though.