5 D. Things to torture Democrat in river (6). The river is sacred to Indians, swap one letter for D(emocrat) (the removed letter is the 'single additional ltter given by wordplay). The answer is the plural of an instrument of torture.
10 Secure inmate's yard (4) The definition is secure, comfortable - so Cosy. It's from Con's Y(ard), dropping the N as per the preamble.