You just need to create the click with the context event, because it is a repeater, like this:
$w.onReady(() => {
$w("#textRepeater").onClick((event, $item) => {
$item = $w.at(event.context) //This creates the context (the item inside the repeater)
$item("#textRepeater").text = "Clicked!" //This changes the text in the context
})
})