do your bit

do a/(one's) bit

1. To do a small amount of something. In this usage, "a" is used between "do" and "bit." I was only able to do a bit of cleaning before your mother called—that's why the dirty dishes are still on the table.
2. To do one's part in a group activity. In this usage, a noun or pronoun is used between "do" and "bit." If you don't do your bit with the slides, our presentation will never be finished on time.
See also: bit

do your bit

make a useful contribution to an effort or cause. informal
The exhortation to do your bit was much used during World War 1, but the expression was current in the late 19th century.
See also: bit

do your ˈbit

(informal) do your share of a task, help a cause, etc: Everyone is expected to do their bit to make the business successful.In reusing this old paper I’m doing my bit for conservation of the rainforests.
See also: bit