Spiderweb
noun
クモ is a spider. Add a nest to it, and you have a spider nest. What do spiders call their nests? They call it a spiderweb (that is, if they can talk).
巣 is a standalone word here, so it uses the same reading that you learned when you learned the vocabulary.
あ、クモの巣ができてる！
Oh, there's a spider web!
空き家の中はクモの巣だらけだった。
The abandoned house was full of spider webs.
うちの家では、クモの巣を見つけても、母が「これは芸術よ！」って言って掃除させてくれないんです。
In our house, even if we find a spider web, my mom says, "This is art!" and won't let us clean it.
屋根裏部屋で、クモの巣が掛かった祖父の未完成の絵を見つけたんです。
I found my grandpa's unfinished painting covered in cobwebs in the attic.