If you have MIDI tracks you should have the tempo set/controlled by the MIDI file. This is assumed. If not, Realband can fix this, but generally this should be OK.

Go to a blank track.
Change type to MIDI
Go to Event List and add a single note at 1-1-0 using channel 10 and Eb2 for the note. Do this again for 1-2-0, 1-3-0 and 1-4-0.
Now you should have one measure of click using a sidestick for the 1-2-3-4 of the first measure (MIDI). Test to verify.
Copy/Paste this for the length of the song. (ProTip: I made a .MID file of this that is 100 measures long to avoid doing the previous steps over and over and now I just import that using Load Scrap feature)

Now you can export/render that MIDI track to an Audio track. Set it up as an audio track in your project and route it to an output that is routed to only the drummer's headphones.
This may require a sound card with multiple separate stereo outputs if you want stereo, but if in mono a basic card can work by separating L/R.
It would also benefit from a headphone mixer. I've used a couple Powerplay PRO-8 headphone mixers for quite a few years without issue. This allows a totally separated feed to the drummers headphones compared to rest of band. <grin>

So a little more info is needed to add more suggestions; what do you have for sound card, mixer and headphone amp? The physical routing is the tough part. The RB part is easy.

I do not work here, but the benefits are still awesome
Make your sound your own!