Recording Click Track (Metronome)

Not yet. At least not easily. There is a feature that is currently being developed that will allow this (track to track routing). No official word on exactly when it will be available though.
 
My personal workaround when I need a "click" track outside of the internal metronome is to just do it using MIDI and a synth (using a drum synth but anything with some percussive sound will do).
 
Just put a MIDI note at every beat (or at whatever interval is needed for you needs for wierd stuff like compound sigs or whatever) for the first bar of the project. Then convert the resulting MIDI clip into a MIDI Groove Clip (which will cause it to repeat when dragged out) and drag it out for as long as needed.
 
You can then Freeze or bounce the track if you want it as an audio clip.
 
The added bonus with this is you can actually add far more nuance to the "click" track if you want by way of intricate "pulse" setups (like using a different hit to accent an offbeat or groove changes or accents in the song). That is of course only if you want to get super fancy but most musicians not used to tracking to a click might find it useful (like if you are trying to get another bandmate to record overdubs or something... it can give them cues and the groove).
 
Cheers.