(...) orbits its star at high speed.
High speed - relative to what? If you mean faster than Earth's orbit around the sun, then either one or both of these affirmatives is true for your planet:
- Its orbit is closer to its star than the Earth's orbit is close to our sun;
- Its star is more massive than the sun.
So how can this planet hold itself together?
The same way that all other planets hold themselves together - through gravity:
According to the definition of planet adopted by the International Astronomical Union in 2006, one defining characteristic of planets and dwarf planets is that they are objects that have sufficient gravity to overcome their own rigidity and assume hydrostatic equilibrium.
Will it need to be abnormally large or made of some exotic materials.
No. It kinda matches what Earth should have looked like in its first half-billion years, give or take a hundred million years.
Seriously. The link above is for the Hadean era of Earth's geological history. Right after that we had the Eoarchean, which is "the first era of the Archean Eon of the geologic record for which the Earth has a solid crust". For some time during the Hadean and its transition to the Eoarchean, Earth had lots of mantle exposed.
So you see, your planet could be made of the same materials as the rock planets from our solar system.
Another interesting thing: Earth's rotation period is actually becoming longer. The slowing of Earth's rotation is mostly loss of energy due to tidal effects from the Moon. Since the Moon was actually formed around the Hadean period, Earth's spin should be much faster back then - young Earth could probably have the same sol as your planet.
I would like to have it relatively close to earth’s gravity, but heavier is ok as long as it is survivable and possible to leave the planet. The planet also doesn’t have to have any sort of atmosphere or surface water, so no worries there.
No problem there. So far what your planet seems to me is like a geologically active, tectonic plated, faster rotating version of Venus.
For something smaller, you may think of Io. It is very active geologically. You could scale it up and give it tectonic plates and it would match what you want as well.