"To defend the currency" means taking actions to protect and maintain the value and stability of a country's currency in the financial market. Full definition
It seems like they are successfully defending their currency at present, at the cost of 15 % interest rates. (alephblog.com)
My guess is the latter, but maybe they have successfully defended their currency. (alephblog.com)
They want to be free of reliance on the dollar, except for what they need to import from the United States or to defend the currency against raids. (michael-hudson.com)