undefining variables for symbolic calculation

Whenever I need to do a quick symbolic calculation involving functions, I need to clear the function variable because Mathcad substitutes the previously defined value of the function. I read on a worksheet that one way to do this is to use the symbolic modifier explicit command, but I think they changed that in the newer version and it no longer works. I know I can just use the clear() and clear.sym() commands but that means redefining the fun_ after, and that's a pain in the neck. Any suggestions? Thanks in advance!

Version: Mathcad prime 10