
1) British traditional history 2) City in ancient Peloponnese 3) Legendary British king
Found on
https://www.crosswordclues.com/clue/oenus

Oenus was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was preceded by Cap and succeeded by Sisillius III. ...
Found on
http://en.wikipedia.org/wiki/Oenus
[city] Oenus (Greek: Οἰνοῦς: Eth. Οἰνούντιος), an ancient town in Laconia, Greece, celebrated for its wine, from which the river Oenus, a tributary of the Eurotas, appears to have derived its name. From its being described by Athenaeus as near Pitane, one of the divisions of Sparta, it was probably situated near the junct...
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http://en.wikipedia.org/wiki/Oenus_(city)
[river] The Oenus (Ancient Greek: Οἰνοῦς, Οινούντας - Oinountas, also called Kelefina) is a river in the Peloponnese peninsula, southern Greece. It rises in the watershed of Mt. Parnon, and, after flowing in a general southwesterly direction, falls into the Eurotas, at the distance of little more than a mile from Sparta. (P...
Found on
http://en.wikipedia.org/wiki/Oenus_(river)
No exact match found.