1
general::
Mean to do or say, as in I don't understand what he's driving at. Today this idiom, first recorded in 1579, is used mainly with the participle driving.
American Heritage Idioms
2
general::
Phrase(s): drive at something
to be making a point; to be hinting at something; to work up to making a point. • What are you driving at? What’s the point? • I could tell Mary was driving at something, but I didn’t know what it was.
McGrawhill's American Idioms And Phrasal Verbs