Quite interesting question. Yes, you are allowed to buy clothes with Bitcoins. Not only the clothes, you can buy anyone. Some of the people already using Bitcoins for online shopping as most of the shopping sites in all countries accepting the digital money to avoid extra charges.
Where precisely is the question here? If you want to buy something with Bitcoin then spend it. It's spendable at most department stores in this area about 65% of them as a matter of fact.