You are a very lucky man. You are getting a nice audio warning from your truck. You must have been nice to it. Most people do not receive ANY warning that there is a grounding issue or the starter is tired. Mine (F250) sits outside. Starter gets covered in corrosion, especially around the connectors. Like Jim says, wire brush everything. Use caution around starter wires. Disconnect posi side from Batt first. This might buy you some time, but eventually the starter will need replacing.

The clank is from the starter motor engaging the engine but not cranking it. Jim gives good suggestions about the electrical connections, but it may also be a weak battery (needing to be replaced if it's a few years old), or the starter motor may be worn out after 12 years.

Classic signs of bad starter solinoid. However, you could try cleaning everything good of corrosion, because it won't cost nothing. Vinegar works good for removing acid corrosion from battery terminals and ends. Usually if it is a bad connection though it won't be one click, it will be a bunch of little clicks together when you try to start it. I'm am positive its the solinoid. I've had to replace a ton of them and that is the classic symptom.

Sounds like a bad connection or corrosion somewhere. Unhook the battery, clean of the connections with a wire brush and hook it back up. Also check the power lead going into the starter motor. Sometimes that can come loose. Make sure that is tight and all of the connections are clean and free from corrosion.

Yes - Clean the battery clamps.