A pearl. They’re found underwater. Removing the head (p) leaves Earl, a guy who could be at your door. Removing the tail (l) leaves pear, a fruit and if you cut both off you’re left with ear, which is with you because it’s attached to your head.
Daughter-in-law. Her daughter’s father is her husband (she’s only been married once and is devoted, meaning she didn’t have an affair). This means John’s son is her husband, so John is her father-in-law, making her the daughter-in-law.
One of these words does not belong, one of these words is not the same. What is it about the words that does not belong? It is more apparent than the first letter not being the same.
Pencil lead. While modern pencils don’t contain lead, that’s still what we call the graphite compound. When real lead was used in pencils it was mined and nearly everyone has used a pencil at some point in their life.