Ref here: SPI - Arduino Reference
Now I'm not an expert (in fact when it comes to SPI, I'm still swimming in a primordial ooze) but the line:
The clock pulses which synchronize data transmission generated by the master.
Seems a bit vague.
I believe that the clock is always generated by the master, and if that's the case, may I suggest it would be a little clearer if it read:
The clock signal used synchronize data transmission. Generated by the master and read by the currently selected slave.
(I'm trying to interface to a board that's arrived without a lick of information and an SMT AT Tiny on in. I don't even know if it's trying to send information so I'm just going to hit it with some clock pulses and see what pops out. I can't find any reference to the !CS on the standard header which has me in a pinch too.)