a state of readiness or watchfulness against attack, danger or surprise

protector

a person who is legally responsible for the care of a child and her or his property

keeper, protector

a guard, e.g. a person who looks after animals in a zoo

guardian

to go round (a place) to see that all is well, to look out for people doing wrong, in need of help etc

guarding; guard

to keep (a person, thing) safe (from danger, enemies, attack)

take care of; guard from harm

a soldier keeping a watch or guard

watcher

a person who watches

lookout

a man who guards property, especially at night

guard