Three wire SPI implementations are highly device-specific. If you're connecting to a slave with a 3 wire implementation similar to LM74, this is usually done with with connecting a high value resistor (typically 10kΩ) resistor from MOSI to MISO. Slave's SI/O pin is connected to this node. MISO and MOSI drives are mutually exclusive as you can see from the timing diagram:
In some cases, you have to use a GPIO as the slave select and implement a custom firmware based timing. Please go through the slave's datasheet and try to match your implementation with its timing diagram.
Another solution if you use an SPI on Port 8 or 9 would be to use SmartIO and the internal Data Unit to route the data automatically to MOSI and MISO. The Data Unit has to be configured as counter that controls the multiplexing of the data via the LUTs. Chip Select should be used to reset the Data Unit.
Third solution and most complex would be a custom component using the UDBs. But this is also the most flexible in case the SPI communication has some special timing requirements.