Set pressure cooker to "sear", add oil, and press "start/stop". When hot, add garlic and onions and cook until fragrant. Add basil and stir to release fragrance. Press "start/stop" to end sear.
Place steamer rack in bottom of cooker. Add fish stock, beer, wine, and water to pressure cooker. Place clams on rack. Squeeze lemon juice over seafood.
Close and lock lid, set pressure cooker to "fish", adjust time to 4 minutes, and press "start/stop".
When done, quick release and make sure all pressure is released before opening. Carefully open lid and discard any unopened shellfish. Using tongs, remove clams and transfer to a deep serving bowl. Pour remaining liquid over clams. Serve immediately.
