Well
noun
A well door is just a well. It's the door that goes into the well hole, making it a well.
This kanji uses the kun'yomi readings for each kanji, for some reason. You learned the kun'yomi reading for both of these kanji as their primary readings already, just watch out for 戸 getting rendaku'd so it becomes ど instead of と.
よく冷えた井戸水を飲むと、冷たいアイスクリームを食べた時のように頭がキーンと痛みました。
When I drank cold water from the well, I got brain freeze like when I ate cold ice cream.