shadow

a spy employed to follow someone and report their movements

follow, usually without the person's knowledge

“The police are shadowing her”

refuge from danger or observation

“he felt secure in his father's shadow”

shade within clear boundaries

an indication that something has been present

something existing in perception only

cast a shadow over

make appear small by comparison

an unilluminated area

a dominating and pervasive presence

“he received little recognition working in the shadow of his father”

an inseparable companion

“the poor child was his mother's shadow”