I assume this comment is because I didn't include the entire sketch.
Exactly.
I'm using the MIDI.h library (version 4.0)
That you got from where?
How to access the Clock value depends on where in the header file that enum is defined.
Whether sending that constant, or not, as "real time" data makes sense, or not, remains to be seen. I have my doubts, but I need to look at the library first.