If your radio has a headphone jack, try plugging in your headset. The speakers in your headset are likely to be better than your radio speaker, and it will help to block our background noise.
Also, are you sure that you are hearing both sides of the conversation? If you're not near the airport then you might only be hearing the pilots and only hearing one side of the conversation makes things very difficult to comprehend!
I never found online ATC to be very clear by the way. They are often monitoring multiple frequencies which is very confusing to say the least!