Once you have “indexed” a Tcl proc (using mktclindex) you can call it by name from any other proc.
You can view the output of mktclindex in $HCISITEDIR/tclprocs/tclIndex That will show you the proc name and the file to “source” (load into memory) when the proc is first called.
That said, there are several different structures for Tcl procs used by Cloverleaf. Usually you will only call a proc of type “Other” from your proc. Procs types like tps, trx or xltp are designed to be called directly from the engine (or testing tool). You probably don’t want to try calling them from your proc.