Like the Río de la Plata vis-à-vis the Amazon

WIDER

Compare the breadth of these two rivers to find the right descriptive term.

The Río de la Plata is a broad estuary, much wider than the Amazon River, which is long but relatively narrow. The clue compares the two, hinting at the answer "WIDER" to describe the Río de la Plata's defining characteristic. It’s a straightforward comparison without wordplay, relying on geographical knowledge.