living only for one's work; devoted entirely to work
Describes a lifestyle or attitude where work is the sole focus, with no other interests or pursuits.
He lives only for his work and has no real hobbies.
I've led a life devoted entirely to work, but lately I've been feeling a bit tired.
仕事人間 is a person who lives for work; 仕事一筋 describes the single-minded devotion itself or a lifestyle.
Compound of 仕事 (work) and 一筋 (one straight line, single-minded). The exact historical derivation is uncertain, but the phrase conveys unwavering dedication to work.