In order to do the static timing analysis(STA), clock definition is the minimum requirement.
Because in PrimeTime, most timing constraints are related to clock.
------------------------------------------------------------------------------------
So, you have to apply the following timing constraint to PT at least,
pt_shell> create_clock -name <clock name> -period <in ns> <clock port/pin>
Give the desired clock period for checking the timing of the netlist.
Then you can run
pt_shell> report_timing
to see the result.
------------------------------------------------------------------------------------