OK, but it is a long fold out page, so in case I can't get it into my sheet feed scanner.
From battery +'ve terminal through a fuse link to a white wire going to terminal B on the key switch.
From C1 on the key switch a black/white wire to the clutch pedal switch (normally open).
Black/Yellow to a (normally closed) PTO safety switch.
Black to another (normally closed) PTO safety switch.
Black/Green to a (normally open) safety switch at shuttle lever.
Brown to starter relay R1, other side of that to ground.
If the click you hear is fairly loud then all of this is probably fine, so it is down to the relay, the starter itself or cables/connections from the relay to the starter or back to ground.
There is a picture of "the relay panel inside the dashboard compartment" (their words).
From left to right reading across the top row, 4 little squares;
R5 R6 R4 R1
R5 RH Road warning light relay
R6 LH Road warning light relay
R4 Reversing light relay
R1 Starter relay
Under that one rectangle and one square, approx under R5 and R6
C3 C2
C3 Glow plug controller
C2 Turn signal/ road warning light controller.
I'm guessing that this is view facing forwards, i.e .from the tractor seat.
To eliminate the relay you could TRY putting jumper cables directly across the starter, with associated risk of shorts and possible fire - your choice. Alternatively you could take the starter out and take it down to somewhere like Autozone for testing.
I tried to get this in my scanner, but it is bound and would need some cutting and messing with. Hopefully this description will do, if not maybe I can get to a MUCH bigger flat bed scanner at the library tomorrow if/when the snow stops.