Fitter error due to 'get_combs' command in .sdc file

I am getting a fitter error caused by a 'get_combs' command in the .sdc file; the get_combs command is part of a create_generated_clock command:

-source [get_combs {blah_blah_blah\

|blah_blah_bla\

|blah_blah_bla\

|blah_blah_bla\

|altera_xcvr_10gkr_a10\

|CHANNEL\

|RX_CLK_MUX_LS.gf_rx_clk_mux_inst\

|reduce_or_0~0~la_mlab/laboutt[6]}]

The create_generated _clock command was automatically generated by Timing Analyzer; the chip built without issues before I added the SDC file. The SDC reference manual I have makes no mention of a 'get_combs' command.

I tied replacing the 'get_combs' with a 'get_pins', which seems to work (fitter is still running) but I don't know what effect that might have on the actual application of timing constraints. Any ideas? thanks.