Add new --clear mode to reduce time spent with a cleared screen

I would like a clear mode which clears the screen only as soon as the first line of output from the re-executed command is produced. E.g. a command that generates a graph or a table, which you want to see update when you edit some files, if it takes a while to render the screen stays blank for however long it takes and then renders the result. I request that this behavior can be changed.