The phrase "a town only" is correct and usable in written English.
It can be used to specify that something is limited to a town, often in contrast to a larger area or other types of places.
Example: "The event is a town only gathering, so please do not invite guests from outside the community."
Alternatives: "just a town" or "merely a town".
I wrote the majority of this blog post about a month ago -- shortly after the shooting in Newtown, a town only 20 minutes from where I grew up in New Milford.
A town only 20 blocks long is desolate at naptime.
We were alone in a spot that had never been a town — only a religious sanctuary.
"People tell me this is a town only interested in pro teams," he said.
Reports from aid workers suggest that the fighting has reached Salayei, a town only 200km (125 miles) north of Monrovia, Liberia's capital.
Banamba, a town only 90 miles (145km) from Bamako, was put on alert after jihadists were reportedly seen in the area.
It is a small town only a few miles from here.' Sitting on a finger of granite, Alesund floats on the North Sea as if a mirage.
She noted that Burnham Market is a fashionable town, only a mile from the North Sea and in the center of what a national organization has designated an Area of Outstanding Natural Beauty, renowned for its sailing, golf and bird-watching.
During the first year of World War I, Göring served with his infantry regiment in the area of Mülhausen, a garrison town only a mile from the French frontier.
TOOTH FAIRY: FEAR OF THE DARK -- When an evil force invades a small town, only the local outcast (Chaney Kley) can save the citizenry.
When that thick slice of Southern ham called "Steel Magnolias" was released in 1989, not much was said about the fact that in a nearly two-hour film, set in a Louisiana town, only two black actors got to speak.
