Meaning of TIE-IN in English
■ noun a connection or association.
↘a book, film, or other product produced to take commercial advantage of a related work in another medium.
↘[as modifier ] chiefly N. Amer. denoting sales made conditionally on the purchase of an additional item or items from the same supplier.
Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004