I don't believe there's currently a way to do this and I'm not sure that there would ever be a way because there's a potential exploit here:
Every new free account gets a number of credits that they can use to buy clothing. At the moment, if you want more than that then you have to buy credits for real money or buy a subscription. If you could transfer clothing to other users then people would be able to sign-up for half-a-dozen alt accounts and buy all the clothing they want & transfer it to their main account - all for free.