I've defined a list of org-mode shortcuts that start with f6.

Example:
f6 i = clock in
f6 o =clock out

Is there a way to see all the available keybindings that begin
with f6?  Sometimes I'm not sure what key I need to type.

When I press f6, then <f6> appears in the minibuffer, waiting for
another key -- is there a key I can press to see the available choices?

If not, how do I pass <f6> to the 'describe-bindings' command when
invoking it using M-x from the minibuffer?
That command takes optional arguments, but I don't know how to
pass arguments to commands from the minibuffer.

Thanks,
--Nate