The biggest thing is that "Clear" shouldn't appear out of nowhere and stretch the other elements. At first, I'll wonder whether I can easily clear these fields or not. And once I enter some data, in the best case, I'll be disoriented as my targets shift. In the worst case, I'll misclick "Apply" when I meant to click "Year". Instead, it should always be present, but disabled when not available.
The word "Year" is clear without it needing to be "yyyy". But if you're concerned about people entering well-formed years, I personally prefer a number field, i.e. a spinner with arrows in usual browser implementations. Some people prefer a dropdown, but that's only practical if you have a few finite years (although plenty of websites ignore this fact and make you scroll through 100 years to choose your birthday...). Another advantage is that you can populate them by analyzing the data; in the case of a dropdown, that also serves as a visual cue to the person of that analysis and what's available.
If you want labels outside the fields, just "Month" and "Year" are fine. Also, if you do so, you could begin the fields on (current month) (current year), or "Any", or a specific value logical for your data.
Here is a pen you could fiddle with that has these ideas.