うちはSBCLだけど、たぶんloadでできる
$ cat hoge.lisp
(defun twice (f x) (funcall f (funcall f x)))
(defun dbl (x) (* x 2))
$ sbcl
This is SBCL 1.3.6, an implementation of ANSI Common Lisp.
(略)
* (load "hoge")

T
* (twice #'dbl 3)

12