How's it hangin' Jedd?
CLC
Clears the carry flag. By "clear" I mean "make it zero".
ADC
Adds the operand to the acc, then adds in the carry flag.
So, having a CLC ADC combo does a simple ADD, assuming the 6502 has an ADD instruction, which it doesn't (MOS-Tek were a bunch of cheap SOB's .
You really ought to know basic stuff like this...