When arranging music, is there a commonly accepted or easy to understand name for an ensemble (be it a trio, duet, quartet, etc.) which contains all of the same instrument? For example, how could you generalize a tuba trio or a clarinet duet?
Ensemble is a reasonable choice already (for example, "tuba ensemble" is an eminently googleable phrase). "Choir" is also another option; for example, a clarinet choir. Either should be easily understandable.
There's no easy answer to this one. Suggestions are either going to be inelegant (exactly what you're trying to avoid) or use specialist language that could be alienating in a more general context. Worse, one could coin neologisms or borrow from other fields, which while providing a pithy terminology would be equally as alienating.
Just to explore the options for borrowing from other fields, one could coin homogeneous ensembles for ensembles of identical instruments (e.g. a flute choir, a dozen celli, &c.) & homologous ensembles for ensembles of like instruments (string quartet, brass choir, "Harmonie", closed consort, &c.). The problem is that these distinctions may require explanation.
Of course one of the issues here is one of definition: is a string quartet an ensemble of like instruments or of identical instruments. I would have a hard time arguing that an alto & a tenor sax are the same instrument, but would call them like instruments. Equally, are the double-reeds homologous, or just the oboes, cor anglaise & heckelphone in one set & the bassoons in another? If all the oboes & bassoons are homologous, what about the sarrusophone?
Clarity & ease of understanding would probably lead you back to more wordy options like larger groups of identical instruments & ensembles of like instruments. Unfortunately for your use case the musical lexicon deals better with specificity than generality.
'Consort' implied instruments of the same type (all string, all wind...) not identical instruments. 'Broken Consort' included mixed types. But, as with most archaic terms, you'll find plenty of examples of varying usage.
I can't think of any generally-understood term that defines a group of identical instruments, other than the specific 'Trumpet trio' or 'Clarinet quartet'. Even then, a 'Clarinet quartet' might include Eb, Bb and bass clarinets. I think you'll have to forego a general term and spell it out!
And, to spell out the answer to your question - no there isn't.
Well-established formations like string quartet are the only ones, which have the benefit of short group name. But the precision you want is difficult to achieve. (Note that string quintet is already ambiguous, since the viola or the violoncello may be doubled, or a double-bass may be added to a string quartet). A piano quintet is more probably a piano combined with a string quartet than five pianos.
A clarinet quartet may address four clarinets as well as a clarinet combined with a string trio.
So you won't get much more precise than piece for two clarinets (which would still leave open, whether both are of the same variant as "clarinet in a", or whether it is for clarinet and bass clarinet.