Answer: binding

AnswerCrossword Clue
BINDINGObligatory.
bindingFabric such as braid used for binding the edges of a piece of material
bindingthe cover and fastenings of a book
bindingThe action of fastening, holding together, or being linked by chemical bonds
bindingA strong covering holding the pages of a book together
bindingA mechanical device fixed to a ski to grip a ski boot, esp. either of a pair used for downhill skiing that hold the toe and heel of the boot and release it automatically in a fall
binding(in Chomskyan linguistics) The relationship between a referentially dependent form (such as a reflexive) and the independent noun phrase that determines its reference