The concept of losing fat in a particular area is called "spot reduction" and, unfortunately, it is not possible. In order to lose fat from a particular area (such as your belly), you need to lose fat overall. You will likely find that when you do so that you lose fat more quickly from some areas and more slowly from other areas, this is largely genetic and some people are luckier than others - for example, there is a fitness rule of thumb that you need to be below 10-12% body fat to have a visible six pack but there are some people who lose fat quickly from their bellies but store more on their backs, which allows them to have a visible six pack at more like 15% body fat.
To more directly answer your original question: yes, you will need a calorie deficit in order to lose fat. This can mean eating fewer calories or burning more calories. Eating healthy foods doesn't mean that you won't be fat - it's quite possible to eat 3,000 calories a day of healthy food but if you're only expending 2,000 calories a day then your body will store the remaining 1,000 as fat.
It's worth noting, though, that losing fat doesn't necessarily meaning losing weight because it is possible to build muscle mass while losing fat. How easy this is depends upon how far into your weight lifting journey you are, it's much more difficult if you've got ten years of organised lifting and eating well behind you but if you have only just started lifting weights (or if you have only been doing so "casually" - without a plan that allows you to track progression over time) then it should be quite attainable.
When I started going to the gym, I didn't know much about diet or about constructing much of a plan for the gym but in the first few months I stayed about the same weight (72kg) but my t-shirts got tighter across the chest and I had to use a tighter belt hole, so I had put on muscle and lost fat but without losing weight.
As a side note, 30 minutes of working out a day will be plenty to get good results if you are dedicated and if you are not eating an enormous quantity of food. I would really recommend buying some cheap digital food scales and trying an app such as MyFitnessPal to rigorously track what calories you're consuming - you only have to do this for a week or two to get a clear picture of how many calories you are really eating and where you could cut some out to reduce it. It was a real game-changer for me when I did this some years ago.
