Let's look at the definition of invert. According to Merriam-Webster: to reverse in position, order, or relationship. This is exactly what we do in chord inversions.
In the following examples we will use the C Major chord.
This chord is made up of the C - tonic, E - third, G - fifth. In the example below the C chord begins in the Root position. That is, it has the tonic, or the C, in the bass position. In other words, the chord begins with the C.
The next cord begins with the third, or, E. This example shows the First Inversion.
The next cord begins with the fifth, or, G. This example shows the Second Inversion.
If you have a C Major 7th chord, it would include the B and would allow for a third inversion.
As you can see, it doesn't matter if the note is in the bass clef or treble clef. The inversion depends on the note in the bass or bottom of the chord.