Kasli has four MMCX connectors which can be used to supply a clock signal for other Sinara cards, including Urukul, yes. The propagated clock signal will be the Kasli's operating frequency, which is usually 125MHz, regardless of whether it was synthesized from the internal oscillator or an external reference.
Kasli also doesn't really support arbitrary external reference frequencies unless you intend to use ext0_bypass, which also directly determines operating frequency, and I wouldn't be sure of the effects trying to run Kasli itself at 30 MHz. Also, Urukul has at least three options for clocking, including its own internal 100 MHz oscillator which requires no reference at all. You might want to read the Kasli and Urukul datasheets.