The reading for this one is mixed. You get the kun'yomi readings for both kanji, even though it's a combo (jukugo) kanji. Since 戸's only reading is the kun'yomi reading you should know it. Also, you should know the kun'yomi reading for 口 as well from level 1. That means as long as you remember that this is a kun'yomi fest over here, you should be able to read this word. Also watch out for the rendaku (also known as sequential voicing). That just means the く becomes the voiced ぐ.
A glove was dropped in the doorway.
I eavesdropped it at the doorway by accident.
There were three pieces of toast in my doorway.