Clock problem

I can't understand what you are trying to do.

From your first sentence I assumed you want clk_out to be half the frequency of clk_in.

This can be done with simple code, like this:

if(clk_in'event and clk_in='1') then

clk_out <= not clk_out;

end if;

Regarding the error. that's normal if you write va <= 1

You defined va as a std_logic vector 3 bits long, so you must use va <= "000"

Anyway, your code seems to be useless since va is not initialized to any other value

and assigned only to 1 when count is 2.

I'd expect at least a reset signal, in order to reset count and va to initial status.