Cyto
Cage is a four-letter word that starts with c and means cell. Or case! Or the 5 letter word Crypt!
The four letter word that means, "I forbid," is veto.veto
The four letter word is dawn.
Cell
cell, crop
CELL, as in cell phone, I guess.
Exit
A four letter word meaning the foundation of something is base.
The word is scam.
Wall
Rend is a four letter word that means to tear into pieces. Tear is also a four letter word meaning to pull apart.
aide