If the element is clickable, make it noticeable and get rid of any uncertainty about the affordance of the given element.
In order to achieve this, you can try different options:
- use a floating button action as trigger: this is the Google Material approach, so it's meant for Android, and it visually helps the user to clearly understand what is a header and what is an action
- make your element look like a button: while you mention a header, is there a reason this header can't have a "button like" aspect? This will indeed take care of the mentioned uncertainty, bar none
- add iconography to support the expected affordance: you can simply add an icon to let the user know the element has a supplemental action
Either way, you should be very careful about this element's behavior. This is a clear indication of a common mistake: confusing content with actions. If this is a header, then it should be a header and nothing else. If it's an action, then make it an action. Content is a semantic description of your site's ... well, content. Actions indicates the particular element will perform some... well, action, and requires user response (touch, click, swipe and such).
Just remember one thing: the clearer and unmistakable the element's affordance is, the better. So, just make a header a header, and if you need any user interaction, add any supplemental action you need for that purpose
Make sure to take a look to this article about Clickable Elements, it has several tips, do's and dont's about this particular subject