In most circumstances, I try to altogether avoid using a dedicated "Clear" button in a software application interface. The action of clearing form fields is a destructive action and while sometimes that destruction is what you want (you actually do want to start over again) there are times that it’s absolutely the last thing you want to do.

On the latter, this is because if you've spent time carefully modifying a set of filters on a big data set then you accidentally hit the "Clear" button, you instantly lose all of that work and have to start from scratch. Smart systems will include a behavioural layer to prevent this (the application will catch your request and ask if you really do want to clear all fields, for instance) but not all software has the same level of user experience thinking built in.

Having said all of that, absolutely there are situations where a Clear button is useful and makes sense to include in your software interface. For me, these are environments where there are three or more form fields and resetting them all one-by-one would be annoying and time-consuming.

The issue I've run into then is deciding on the content of the button itself. Should it be an icon or text? If it's an icon, what should that look like? How do you create and design an icon that universally says Clear? And, speaking of that label, should it even be Clear? What about Reset or Start Over?

In the end, you're going to have decide for yourself because different cultures and settings will have unique ways of interpreting the meaning behind an icon. So, to be safe, I’d just use simple text and present it in the chosen language of the user.

A related example of an element from one of my interface designs is below:

With this particular software, I followed my own advice and chose to avoid an icon and just use a text label. With it, I put a verb + noun combination together where Clear is the verb and Field(s) is the noun. In this case as well, the fields themselves are jump lists that automatically respond to user input; that is, instantly filter the data below based on choices above.

In my mind, "text" is the simplest, most direct way to deal with destructive button like Clear. Other, less-powerful buttons can safely use an icon as a label (as long as you combine it with a tooltip as a basic usability back-up measure) but for important actions, I’d really recommend plain old text.