Maybe it helps to consider dark matter. What we have is effectively a placeholder definition based on its observable effects. We don't know if it's WIMPs, axion-like particles, or even some alternative framework for gravity. But we have enough to state meaningful questions about it and iterate toward understanding from a number of directions using a combination of hypothesis, data and experimentation. Finding out what it truly is would be the culmination of research that settles the question rather than something to be stipulated at the start.
So depending on how you look at it, you already have a working definition of consciousness sufficient to organize research, we already have made real progress of the kind that should be impossible if definitions were really dealbreakers, and having "a definition" in the complete sense is something you would never have up until the point the question was settled once and for all, which happens at the end of research rather than the beginning.
I see Wittgenstein mentioned more often in these parts which is awesome, and I think the best Wittgensteinian attitude to adopt here is to turn the tables on this whole question and refuse to agree that there's such a thing as a question of definition that stands between us and research progress.
