Solution: There are nine across theme entries that are current or former FORD models. 15A, 20A, 22A, 26A, 37A, 43A, 46A, 49A, 59A. The first words of the clues for these entries, in order, are: Synonym for theme and vehicle class that it makes. A synonym for the theme (FORD) is CROSS OVER, which is also a class of vehicle that FORD produces. The answer is CROSSOVER.
Woah, cool. I didn't even catch the part with the first words of the clues- I tried looking at the first letters of clues, but they didn't do anything. But I knew all the models, and was already thinking Ford = cross a river because of your puzzle image, so I just typed Ford Cross into Google and it gave me Crossover. Made sense, so I went with it. Wish I had noticed the extra part with the clues!