So, I'd say that's a clash.
Depends on how you define the word. As I set forth with my reference to a Newton's cradle, I tend to think of a clash as two objects moving towards one another. Much like two cymbals coming together. Definition 2 from dictionary.com states: to come together or collide, especially noisily: The cymbals clashed. Likewise the same source indicates that the word originated in the late 1400's from clap and dash.
Now if we are talking about two objects, both in motion, or in this case relying on motion as a primary means of generating in power you have a clash. Is there a combination of energy, absolutely. It is undeniable. However, the larger person, or person with better technique will win.
What I am referring to is more like one object impacting another object resulting in a deformation of the first object (an unbalancing effect) due to compression of the second object transferring forces into the ground. In this case, the energy of the first object, was combined with the weight/mass of the second, rebounded off the ground and moved the first object rather than both. To me this tends to be the stereotypical definition of aiki, yet this kind of power tends not to be what is practiced.
I don't believe its because you inherently need to be stationary to generate it, just that the larger component of the generated "aiki" is from transfer into/out off the ground, rather than rotation, explosive movement, weight shift, momentum, big circles (essentially what powers technique). This is more or less what the ki society tests are supposed to show, but I won't comment on whether or not they are practiced properly or not.
This is also a differentiator, in that if it is simply the result of two bodies moving together, outside of waza, then the person who can generate more musclar effort or has larger mass will win. Aiki does not require this, and thus a 90lbs woman, can hold off a 200lbs man as the 200lbs man can not access the ground. Anyone who has been to one of the Aunkai seminars and has had hands on with one of Akuzawa sensei's female students can attest to this.