This question warrants some terminology clarification. “Matter”, “antimatter”, and “charged” all get used in multiple ways depending on context, so your question could be answered in multiple ways.
There are a handful of fundamental particles of nature that we know about (electrons, quarks, photons, … everything in this table). Those entities are usually called “particles”, and they have “anti” counterparts that are usually called “antiparticles”, although in some cases the particle and antiparticle are actually the same entity. To confuse things, though, sometimes these two sets are called “matter” and “antimatter”. To confuse things more, sometimes only the quarks and leptons are called “matter” (and the antiquarks and antileptons called “antimatter”), with the bosons on the right of the table being left out of the definition.
These fundamental particles can join up to make composite particles. The most familiar are the proton (made of two up quarks and a down quark) and the neutron (made of two down quarks and an up quark). Neutrons and protons can bind up via the strong force to form nuclei, and these nuclei can capture electrons to form atoms. In certain contexts, one would use “matter” to mean these nuclei or atoms and would use “antimatter” to mean analogous nuclei or atoms made from antiprotons (made of antiquarks), antineutrons (made of antiquarks), and antielectrons (a.k.a. positrons).
So, can uncharged particles combine to form matter? Depends what you are interested in. A lone neutron could be called matter, and it is neutral. A hydrogen atom is neutral, and two of these can combine to form H[sub]2[/sub] which is undeniably matter. On the other extreme, gluons are electrically neutral yet we expect they can form bound states with each other. Whether you want to call the resulting “glueball” matter or not is just a choice of definition. (Probably it’s not what you have in mind.)
The gluon example gets us to how “charged” can mean different things. In everyday language, “charged” means “electrically charged”, but it’s not the only type of charge there is. An electron binds to a proton to form hydrogen because both have electric charge. A proton and a neutron bind to form a deuterium nucleus because each is made of things that have “strong” charge. (Protons and neutrons have no strong charge themselves, but the strong charge of their constituents quarks bleeds out, analogous to electrically neutral atoms forming molecules because the components of the atoms are electrically charged.)
Dark matter is electrically neutral, but it may have other charges. There are many viable theories in which dark matter particles interact with each other through their own dark-sector forces(*), forming dark atoms. These dark atoms could then reasonably be called “dark matter”, except that the term “dark matter” is already taken to mean generically anything that does what dark matter needs to do cosmologically and astrophysically.
(*) To make the connection explicit: forces and charges are related. Things that have strong charge interact via the strong force. Things that are electrically charged interact via the electromagnetic force. Some new “dark charge” on dark matter would lead to a dark force.
Given the above, I’ll reword your question to what I think you are asking: “If a sufficient quantity of antiatoms (made of antineutrons, antiprotons, and antielectrons) were found together, would they clump together to form antiplanets, antistars, antigalaxies…?” Yes, as far as we know. We haven’t seen any large anti-clumps out in the universe (which is a story all its own), but they should behave basically the same as if they were made of matter.
Not exactly. Particles have antiparticles, so dark matter particles could reasonably have “anti” versions of themselves. But whether you call these entities anti-dark-matter or dark antimatter is just a terminology choice.