To rotate a point \((x, y)\) clockwise about the origin by 90 degrees, you use the following transformation:
\[ (x, y) \rightarrow (y, -x) \]
For the point \((-4, -6)\):
- \(x = -4\)
- \(y = -6\)
Applying the transformation:
\[ (-4, -6) \rightarrow (-6, 4) \]
Therefore, the new point when \((-4, -6)\) is rotated 90 degrees clockwise about the origin is:
\[ \boxed{(-6, 4)} \]