Non Driver, you're right to be confused. The use of the expression "Westerly runway" is a nonsense and is only used by the (far too many) people who don't think about making comprehensible PAs. The only way a runway can be the westerly one is if two are more are arranged north/south. It cannot, and does not mean pointing in a westerly direction in non-aviation English.
It is an expression that I guarantee not one pax in 100 will understand.
Don't use it!
(What's wrong with landing in a westerly direction, or from the east, as if it matters. Come to think of it, how many pax even know where west is?)
Think before you make PAs with technical or aviation jargon!