This is the 4767th most frequent Russian word.
западным
"Западным" means "western" in English.
Here, 'западным' is an adjective describing 'границам' (boundaries), indicating their location pointing west.
Мы направлялись к западным границам страны.
We were heading towards the western borders of the country.
In this sentence, 'западным' modifies 'берегу' (bank) to indicate its position, situated west with respect to the river.
На западным берегу реки раскинулся город.
On the western bank of the river lies a city.
Here, 'западным' describes 'агентствам' (agencies), suggesting their geographical origin or alignment related to the west.