Send him (her, you) a card

Hackefalta is a very common sentence pattern, that is, what is missing is missing. Mandarle una tarjeta de Felicia cion is a phrase, which is used as a noun here and is singular. So HACE is used to represent the third person singular. It is the matter of "sending him a card" that "has not been finished".

For example, Maas, a college student in mehace falla. I need to learn more (I need to learn).