It's not possible to write CL's loop macro per-se (tcl does not have macros, but commands/functions which are executed each time and there isn't an distinct mac

It's not possible to write CL's loop macro per-se (tcl does not have macros, but commands/functions which are executed each time and there isn't an distinct macroexpansion/compilation phase), but it's certainly possible to write something that essentially matches behavior and user interface of loop (and it's probably significantly easier to do than writing loop in CL).