"an indispensable skill" is correct and usable in written English.
You can use it to refer to a skill that is essential and necessary. Example sentence: Learning to use computers is an indispensable skill in the modern world.
Given that the city is home to close to 200 nationalities, the extent to which one can communicate and interact with people from varying cultural backgrounds is an indispensable skill.
Not being able to monopolize an indispensable skill and thereby realize their interests at the workplace and through the market alone, workers in such industries needed unions capable of mobilizing mass solidarity across occupational boundaries.
Ultrasound (US) guided central vascular access is an indispensable skill for physicians.
The ability to perform emergency open or percutaneous suprapubic catheterization (SPC) is an indispensable skill in medical practice.
If you possess the one indispensable skill – battering and blustering your way to the top – incompetence in other areas is no impediment.
But the practice has been revolutionized in recent years by the addition of an unlikely yet indispensable skill-set: literary finesse.
In such places, shifting hourly from one language and scene to another was an indispensable life-skill.
These days, the indispensable skills of a globe-trotting artist are as much managerial as technical.
This strategy yields a shorter SAT while preserving its current strength in assessing two indispensable skills for academic success writing and mathematics.
Staring was just one of the indispensable skills that were drilled into Cassidy and his comrades, years before, by Bill Django Jeff Bridgess), who vowed, "We must become the first superpower to develop super powers".
When certified and endorsed by the community those indispensable skills will lead to "universal solutions" and powerful changes for the best of the world.
