In Eshell, how do you alias to a lisp function?

I have noticed something like: alias ff 'for i in ${eshell-flatten-list $*} {find-file $i}' for binding aliases. How do you bind aliases for lisp functions? For instance, I'd like to find file then switch to other window, in lisp syntax.

`alias cls ig-eshell-clear t` aliases `cls` to call my custom function with parameter