The phrase "one's only job" refers to the main or sole responsibility or task that is assigned to someone. It signifies that this particular job is the most important or the primary duty that they have to fulfill. Full definition
Looking for a job is not only a job in and of itself, it's expensive. (distinctiveweb.com)
I received some advice from someone whose only job in life is to take money from «greedy» landlords and give it to «deserving» and «abused» tenants. (biggerpockets.com)
We believe in the transformative power of the everyday dog or cat — «ordinary» companion pets whose only job in life is to love without limits. (petsforpatriots.org)