Trip? Trek? Tour? Rove? I am not sure, but these are what I looked up so...
The four letter word that means, "I forbid," is veto.veto
trip
The four letter word is dawn.
Trek!
Exit
A four letter word meaning the foundation of something is base.
The word is scam.
Rend is a four letter word that means to tear into pieces. Tear is also a four letter word meaning to pull apart.
aide
Fast
step
asea