The foundation of something can be described as its "base." The base of an object or concept is its fundamental support or underlying structure. It provides stability and strength to the rest of the entity.
The four letter word for repairing something is mend.
have
One such word is evil.
vase
grip
base
The four letter word for repairing something is mend.
have
grip
seat
A four letter word for something a violinist needs could be Bows.
Urge
One such word is evil.
to mend
vase
grip
lose