Noun has 2 senses

• instancy(n = noun.attribute) immediacy, immediateness, instantaneousness - the quickness of action or occurrence; "the immediacy of their response"; "the instancy of modern communication"

Derived form adjective instant₁

• instancy(n = noun.attribute) imperativeness - the quality of being insistent; "he pressed his demand with considerable instancy"

Derived form adjective instant₃