Darek,

First of all you have to get SPI-master mode by setting the MSTR bit in SPCR (and SPR1,SPR0=00 for Fosc/4).

Secondly, to start the SPI clock you have to write to SPI data register some data, 0x00 for instance.

Then you can see the clocks I hope(:-).

Cheers,
George