tie in

Short definition from Wiktionary

Verb

1. 1
   To fit in or harmonize (with something).
2. 2
   For a local station to begin broadcasting an ongoing network transmission.

Noun

1. 1
   Alternative spelling of tie-in.
2. 2
   Something that is related or connected to another thing.
3. 3
   An authorized product based on a media property, such as a film or video game, by way of cross-promotion.
4. 4
   An association or connection between things.