This depends on the device. Outputting the clocks to pins is a capability that was added as new generations of the PSoC were created. See the OSC_GO_EN register description in the Digital Clocks section of the PSoC Mixed-Signal Array Technical Reference Manual (TRM) for a description of how to set the clocks to drive the Global Out busses. Once routed to a Global Out bus the clock can be routed to a pin.
21xxx - VC1, VC2 and VC3 can be routed to pins
24xxxA - VC1, VC2 and VC3 can be routed to pins
27xxx - clocks cannot be routed to pins
29xxx - VC1, VC2 and VC3 can be routed to pins
Note:.A clock of maximum 12 MHz can be routed to any GPIO.