Wiktionary
top-priority
a. 1 Of the highest level of importance 2 To be done before doing anything else.
Usage examples of "top-priority".
He would permit Miller, as author of the top-priority measure, to read out to his assembled colleagues and the gallery, “Resolved, that Douglass Dilman, President of the United States, be impeached of high crimes and misdemeanors in office.
There's a lot of evidence that both the American and the Soviet governments take the subject a damn sight more seriously than they let on in public and are conducting top-priority studies to understand and isolate a whole range of esoteric phenomena, from levitation and Kirlian photography - a film process that reveals the human aura-to telepathy and teleportation and psychokinesis.