Holding a strong, well formed from lever is something of incredible athletic skill; it demonstrates a core and lat strength beyond normal people. And like any advanced athletic skill, the front lever can be built up to throughprogressions and consistency. A few exercises that you will want to use to progress to a front lever are:
Scapula Pull Up
Wide grip pull up
The front lever is an undeniable test of your isometric ab strength; naturally, having strong abs is a must. Building up to a 30 second L-sit will be a good foundation for this exercise.
Scapula Pull Up
The scapula pull up, as seen in the video above, is a pull up done by depressing your scapula while holding the pull up bar, which strengthens many upper back muscles, as well as the spine and lower lats. The support strength that your mid back will develop will be essential for crisp form in holding the front lever.
Often used as a neck exercise, the wrestler's bridge is a fantastic back exercise as well. This works many of the muscles the scapula pull up works, with a stronger emphasis on the mid to lower back. This will further develop your core strength to hold the front lever.
Wide Grip Pull Up
Lats. Lats and lats. This exercise will help build the hand and lat strength to help depress your scapula when doing the front lever, and it will give you lats. Did I mention lats? Yes, yes I did.
This is an exercise too, in fact the most important of all those listed. Keep trying and don't give up the exercise. It may look shaky in the beginning, as the above front levers do. You may take some time to build up to the front lever, but as long as you are consistent, you will get there.