Steps to reproduce:
1. Open attached ’ClipSelection.zip' Unity project
2. Select ‘Timeline’ in Hierarchy
3. Go to Window->Timeline
4. Attempt to select an animation clip by clicking on its edge

Expected results:
Only the clip is selected
Actual results:
Both the clip and the track are selected

Reproduced in: 2017.3.0b1, 2017.3.0a7, 2017.2.0b11, 2017.1.1p2, 2017.1.0b1

Note: There is a very narrow area you can click on to select both the animation clip and the track it is on when clicking on the edge of a clip where the cursor changes from the horizontal resize to normal