I was just looking on the Internet and found that descriptions of clamp-on multi-meters are fuzzy at best. Many of the so called AC/DC clamp-on meters measure only AC current with the clamp, so make sure you know what you're getting. Also, you want one that measures as little as .01 amps. I've had one that measures DC current with the clamp for at least 10 years, but there is no name brand on it!
Worst case, you could remove either battery cable and connect a standard multi-meter (set to measure DC current) between the cable end and the battery terminal. Just don't turn on the ignition or any accessories! Some meters have a dedicated fused input jack for 10 amps. Others might be able to handle only 100 milliamps or so.