Saloon at the Nag's Head possibly used for a dance (4)

(Source: London Evening Standard)

General meaning ⇒ somewhere or something that can be used for a dance

"saloon" ⇒ another word for a saloon? ⇒ e.g. a "bar"

"the Nag's head" ⇒ the head of "Nag's" ⇒ the letter "n"

Answer ⇒ barn