Something you can eat that has a 4-letter name: Food or ... - Meat - Fish - Soup - Corn - Peas - Dill
fork
You grip something tightly.
base
done
Ask your teacher to help you do that
Beer has only four letters. Milk, java, soda and wine have only four letters.
A door is an opening.
mend
threat
grip or grab
to put something on top of a tree? 4 letters? ummm how about STAR