The phrase "do duty" is correct and usable in written English. It is typically used in the sense of someone or something fulfilling an obligation or duty. For example: "The police officers do duty to protect and serve their community.".
The "Scouting Spirit" gets plenty of ink, as do "duty to country" and completing "good turns".
It can also do duty as a ledge for storing items in a kitchen, bathroom, children's room or foyer.
Of course, most dogs do duty as family pets, and that role should not be made light of.
Occasionally, contemporary reconstructions do duty for combat shots, and, perhaps more often, genuine footage is deployed in inappropriate circumstances.
The film reveals that a large number of extraterrestrials do duty-free shopping before leaving the planet and that the World's Fair grounds in Flushing are not going to waste after all - Monday at 8 p.m. on Channel 4. And if that isn't enough Barry Sonnenfeld for you, try a double feature of THE ADDAMS FAMILY (1991) and ADDAMS FAMILY VALUES (1993).
Does duty come before passion?
Ms. Belforti also does duty cleaning the town hall bathrooms.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union