'a trick or device intended to attract attention, publicity or trade' :)

A 'trick' is not the first thing that comes to my mind. It doesn't need to be either a trick or related to publicity. It can be 'a (novel) device intended to attract attention' (or business). But it's slightly derogatory to call something a 'gimmick.' Like it's cheap. As opposed to an 'innovation.'

A gimmick is a piece of magic. Since magicians always employ deception to make their tricks seem real, you imply some degree of trickery or fakery when you call something a "gimmick". However, it is not necessarily something bad, just as magicians are not bad. You can employ a gimmick merely to be funny or to make something work. For example, if the door to your refrigerator won't close, you might attach some heavy object to the top of the refrigerator to lean against the door to make it close. That would be a practical gimmick. The thing that makes it a "gimmick" rather than a "fix" is that it is so ridiculous.

Something (a device or trick) used to attracted attention