President Barton received the outfit as a gift from a foreign dignitary who did not understand that he could not humiliate someone like Clint Barton by making him wear such an….unusual suit. Rather, the suit was presented and Clint’s eyes got huge and he stripped down to his boxers then and there (Steve mostly stood in front of him) and put it on, delighted. Then he gleefully wore it to his next like, eight public appearances.
Fun fact: a lot of couture clothing is only meant to be worn once, which means that while it isn’t shoddily made, it can be rather fragile. This suit was in no way meant to take as much wear and tear as Clint put into it, not to mention the dry-cleaning, and the result was that the suit literally fell off him as he was leaving a press conference one afternoon.
The most direct result of this is that now the world knows that at some point, he’d had a pair of underwear tailored to match the suit.