And this is a...
After a while I decided on waterbuck because of the colour and fur. Other contenders are reedbuck and to a lesser extent, topi. It can't be a hartebeest: both sexes have horns.
by areinders moderator
This is a Thomson's gazelle, you can see the black stripe at the right lower edge of the image. Also, the second, more narrow "ear" in the first frame is actually a horn. You basically just see half of its head. Waterbucks are larger and much more fluffy. Topis and hartebeest are also much larger.