Well, I'll give it a shot. Distance isn't made of particles or waves. Is distance physical?
Time, like distance, isn't composed of particles or waves, but is used to describe intervals between physical events. This is why time is referred to as a dimension, because, like distance, two events can be separated by it. And this simple fact is the reason time (and distance) are useful concepts.
And any useful definition of time will be very similar to a useful definition of distance, in the sense that both are intervals between "physical things", not "physical things" themselves.
So, yes, time is a dimension instead of a substance.