The phrase "a certain pub" is correct and usable in written English.
It can be used when referring to a specific pub without naming it, often implying that the reader or listener may know which one is being referred to.
Example: "I met my friend at a certain pub in the city that we both enjoy visiting."
Alternatives: "a particular pub" or "one specific pub".
A few months later we gathered at a certain time outside a certain pub, dressed according to a certain theme (Arabian Nights, a choice so crushingly unimaginative that I should have considered myself warned there and then).
Well, it turns out the millionaire, J Cochran Darrow, has discovered how to time travel, and is planning a lucrative trip back to the beginning of the 19th century and a certain pub where Coleridge gave a lecture, for which literature enthusiasts are shelling out top dollar.
Almost all these patients frequented a certain pub in Rotterdam, and the TB control nurses found that patient X had been ill for several months and also visited this pub.
"Venture into certain pubs in Hackney on a Friday night and it looks like an Allen Ginsberg convention – but without the poetry.
At certain pubs, indeed, queues at Sunday lunchtimes begin before the pubs open, and hundreds of people can cram into a few small rooms to sing.
Unemployment was high in those neighborhoods and the bitterness was tangible; students weren't supposed to go to certain pubs.
There were certain pubs everyone knew would serve past closing time, or – more thrillingly – might actually let you in after 11.
The effects of binge drinking are all too obvious to anyone brave enough to take certain trains late at night, or to stand outside certain pubs at closing time, or to venture into town and city centers across the country at midnight on a Saturday.
If you drop the F bomb in certain pubs in the UK, you could now risk being barred.
For instance, the other day I learned that there are certain pubs throughout this land that allow dogs in, but seemingly have no room at their inns for jackals, foxes, wolves, or any other member of the canis family.
The weirdest place I've actually visited is probably a certain Scottish country pub that shall remain nameless.
