Draw upon is a phrase that means to USE something as a resource. The three crossword solutions for this phrase are TAP, USE, and TAPINTO. TAP is an abbreviation of the verb 'to TAP, ' which means to lightly hit or strike something. USE is an abbreviation of the verb 'to USE, ' which means to make USE of something for a purpose. TAPINTO is a combination of the words 'TAP' and 'INTO, ' which means to access or draw from a resource.