think so, you cant have entities connected with the void, so:
- put a clip-shadered wall behind it to cover it
or
- make an inner, thin, invisible wall (with full clip) and make it func_static
or
IIRC - slick shaders are non-wallwalkable (M I rite?), so you could make your own shader that uses desired texture + add surfaceparm slick
code to make it slicky (sorry dont have time to write a shader for you)
try that