I took a couple passes through the search, but either turned up a million hits or not what I was looking for - seeing as "clock" is interchangeable with speedo/tach references.

I've decided I don't need the timepiece on my dash; I don't mind leaving it on there once it goes dark, but I don't need to have it being a constant drain on the battery, and - since I don't think it works properly anyway - I'm concerned that it's turning itself into a bigger drain than normal by becoming an open circuit. Is there a simple way to disable power to it?

Im pretty sure its the orange wire that feeds the clock , either snip the wire or ( probly better ) pull the orange wire out of the multi plug at the dash (and insulate the end ) .
The clock is known to fail and draw excess current

According to the wiring diagrams:
On the 750 it is the pink wire from pin1 of the big connector at the centre of the dash which comes from the voltage regulator, piggy backed on to the red wire from the battery +ve.
On the 906 it is the same but the wire is orange.
On the 907 the wire is also orange but comes from fuse no 1 (permanently live).

On my own 907 I just takes fuse out if I'm parking it up for more than a day or so but 750 and 906 owners don't appear to have that option. So if you want to take the clock out it would seem that cutting the wire at the dash connector would be best.

Beautiful! Thanks for the infos!