Preheat the oven to 450 degrees F (230 degrees C). Line a rimmed baking sheet with parchment paper or a silicone mat.
Slice chicken breasts into 3 or 4 tenders about 2 inches wide.
Toss potatoes with olive oil to coat; sprinkle with 1/3 the sage. Season with salt and pepper. Lay potatoes in a single layer on the prepared baking sheet.
Bake in the preheated oven until golden, 20 to 25 minutes.
Combine bread crumbs, Parmesan cheese, and another 1/3 the sage in a shallow bowl.
Zest, halve, and juice 3 clementines. Add enough lemon juice to make 1/2 cup of citrus juice. Quarter juiced clementines; reserve.
Combine citrus juice, melted butter, Italian seasoning, and 1/2 teaspoon garlic powder in another bowl. Dip chicken tenders one at a time into the juice mixture; coat with the bread crumb mixture.
Toss broccoli with the remaining juice mixture and sage.
Reduce oven temperature to 400 degrees F (200 degrees C).
Scrape potatoes from the pan using a spatula; toss slightly to make room for chicken and broccoli. Add the coated chicken and top with 2 sliced clementines. Add broccoli in a single layer. Sprinkle remaining garlic powder on top; season with salt and pepper. Scatter reserved clementine quarters around the pan.
Bake in the preheated oven until chicken is golden and broccoli is crispy and browned on the edges, about 20 minutes. An instant-read thermometer inserted into the chicken should read at least 165 degrees F (74 degrees C).