Clint Barton has been deaf in the comics for a while, but the Marvel films haven't done anything to address that disability when it comes to live-action. What's interesting is, they could be making Clint deaf in the upcoming Disney+ show.
As pointed out by some fans, in the set photos of Hawkeye, you can actually see that Jeremy Renner is wearing a hearing aid.
You can check out the close up here.
While it's possible that it could be a piece Renner has to wear so he can receive stage directions more efficiently, I like the idea that this has something to do with Hawkeye's arc in the show. With the series set to introduce Kate Bishop as Clint's protégé, it would make sense that Clint would have some kind of disability that would prevent him from staying with the Avengers and proceed to find a successor.
With all the other major heroes having signed off in the films, Hawkeye needs a better sendoff than just dying; and losing his hearing could be his out. With Yelena Belova expected to take on the Black Widow mantle from Natasha Romanoff, it would only be fitting for Hawkeye to also give the reins to someone younger and more capable.
Of course, this is all just speculation from the fans' part. Hopefully, Disney comes up with an official synopsis soon, as this show could be looking to release late next year. My guess is we get our first teaser when Black Widow finally comes out in May 2021.
In the meantime, MCU Phase 4 launches when WandaVision hits Disney+ on January 15, 2021.