Actually, the buck stops with the POTUS. He can order and stop investigations and prosecutions. Obama did it with immigration enforcement , investigations and prosecutions.
I don’t know what’s up with Trump. While he has the power to do so, he cannot politically get away with firing Sessions and the special prosecutor, and appointing a new AG and putting him/her in charge of the Russia investigation.
He needs to leave his loyal ally Sessions alone and order an investigation of Clinton if he wishes ( there are reasons not to do so, as it would appear to be vindictive). He needs to hope the special prosecutor over steps his commission and gives Trump good cause to fire him. He does not have good cause now.
Hope is not a plan.