Try setting the variable to null:
You can read more about this under section "2.1.8. Context variables" in the documentation.
I think the better do like this:
because "set" does not remove variable.
Setting an @In(create=true) @Out(required=false) var = null is probably the easiest way to clear a variable and have it be recreated on next invocation.
You can use the Contexts methods explicitly, but they add LOC and greater coupling to Seam internals.