The clutch safety switch--if your car has it, requires you to push down the clutch pedal to start the car, and works just like the neutral safety switch for an auto trans
Here's how it works. The older (69) cars with a stick had THREE terminals on the firewall mount starter relay.
The largest stud goes to battery
The other exposed screw goes to the starter
(Jump those two to crank the engine)
The third "push on" terminal goes to the "start" position of the ign switch, and engages this relay for start
Additionally, if you have an auto trans, or the "clutch start switch" there will be a FOURTH wire--a push on connector--on the relay.
With an auto trans, this wire is grounded when the trans is in neutral or park, allowing the relay to operate
With a stick, and the "clutch start" switch, you push down the clutch and that switch grounds that relay terminal.
My book shows the wire to the clutch as a separate (push on, dark green) going through a firewall grommet by itself. To test, remove the push-on wire from the relay, and GROUND that relay terminal. The car should crank
If not, see if the other push on get's power when the ign switch is in "start." If you have power there, and the relay does not pull in, you have a bad relay.
One of the first things I did when I got my '70 RR was to bypass that clutch switch.