Last two, and I can't make any sense of them
1a Number officer beat soundly (7) --C-I-E
1d As a body, mounted action(7) --R-A-E
The across one I wonder if the definition is number, but perhaps as a verb, with something to do with a word that sound like beat
The down one, drivers=cars? but mounted action, something to with horses?
No idea really, so any help gratefully received.